German Chancellor Angela Merkel's office sought to calm nerves after she suffered a second bout of uncontrolled trembling in just over a week, saying the veteran leader was en route to Osaka on Thursday as planned for the G20 summit.

Merkel's latest health scare came just hours before she was due to board the plane for Japan, sparking new questions about her health.

On Thursday, a German government spokesman said Merkel would not cancel any appointments in the next two days - saying 'The chancellor is well.'

Merkel's spokesman Steffen Seibert later tweeted she was on the way to Osaka for the G20 summit, and that 'numerous bilateral talks with other leaders are planned'.

The 64-year-old Chancellor's arms and body could be seen noticeably trembling as she met Germany's President Frank-Walter Steinmeier today.

Chancellor Angela Merkel was seen shaking as she met President Frank-Walter Steinmeier in Berlin

The German Chancellor was seen folding her arms as she attempted to contain the juddering motion

For around two minutes, she continually folded her arms in an apparent attempt to stop her hands and body from violently juddering.

Close-up footage showed the difficulty she was having trying to keep the quivering under control as she gripped her arms together.

It comes 10 days after she blamed dehydration for the shakes she suffered during a meeting with visiting Ukrainian President Volodymyr Zelenskiy.

WHAT IS CAUSING ANGELA MERKEL TO SHAKE? German Chancellor Angela Merkel has been caught on camera shaking again, for the third time in a month. In the first episode, on June 18, she blamed dehydration for her trembling as she stood in the sun in Berlin next to Ukraine's new president Volodymyr Zelensky. A Merkel spokesperson on June 27 offered no reason for the second incident and claimed she was 'fine' after footage showed her shaking while standing next to president Frank-Walter Steinmeier. An over-active thyroid? Dr Sarah Brewer, a GP and medical director of Healthspan, told MailOnline Merkel's shaking could be caused by having an over-active thyroid. The condition is 10 times more likely to strike women than men, according to the NHS. Side effect of medication? Dr Brewer added that shaking could be a side effect of some medication. The US National Library of Medicine lists 17 different drugs that can cause the shakes, including caffeine, antibiotics, antidepressants, alcohol or nicotine. Experts are divided over the suspected cause of Angela Merkel's mysterious shakes. One said the jolts were 'not a sign' of Parkinson's, which is often associated with tremors (stock) Low blood sugar? Shaking, which is uncontrollable, can also be a sign of low blood sugar - a serious complication often seen in diabetic patients. Essential tremor? The shakes can also be caused by a fever, fear, stress or a medical condition called essential tremor. The neurological disease strikes up to four per cent of people over the age of 40 in the UK, data suggests. It is unclear how common it is in Germany. Orthostatic tremor? After watching the footage of Merkel shaking the first time, Peter Garrard, a professor at St George's, University of London, said her symptoms 'seem to fit with a diagnosis of orthostatic tremor' - a rare neurological condition. When asked again on June 27, he told MailOnline: 'I still think it’s orthostatic tremor.' The disorder, previously referred to as Shaky Legs Syndrome - according to orthostatictremor.org, tends to strike people in their sixties. Merkel is 64 - she turns 65 next week. Patients often suffer with tremors in one or more parts of their body, which is often worse when they stand. The progressive disorder generally causes 'shaky' or 'frozen' legs, which usually disappear when the patient sits, walks or lies down. Stress can make the shakes worse, which then becomes a vicious cycle as tremors cause the patient to become increasingly uneasy. Or the tremors, which can last just a few seconds, can come on for no apparent reason. Over time, the condition can cause fatigue, pain and immobility. There is no cure but drugs like Clonazepam can ease the symptoms. Walking aids like scooters, sticks or even wheelchairs in extreme cases, may eventually be required. An infection? Dr Mike Fitzpatrick, a GP, told The Telegraph the body often shakes when fighting an infection. This helps to raise the body's temperature to 'kill' an invading bacteria or virus. 'Rigors tend to last a few minutes and then once the heat is generated, you’d be right back to normal,' he said. However, Dr Philippa Kaye, a London-based GP, told MailOnline that she would hope any infection Merkel may have had 'would have been treated by now'. What experts say definitely aren't causing Merkel to shake Parkinson's - Ley Sander, a professor of neurology at University College London told MailOnline the shakes Mrs Merkel had was definitely 'not a sign' of Parkinson's - a condition often associated with tremors. Dehydration - Dr Paul Jarman, a consultant neurologist at University College London Hospitals NHS Foundation Trust, told MailOnline: 'What I can say for sure is that it was not due to dehydration.' The NHS does not list shivering as a known symptom of dehydration - when the body loses more fluid than it takes in. Advertisement

She later claimed to have felt better after drinking some water.

During today's incident an aide rushed to her side to offer her a glass of water, which she declined.

Berlin is in the throes of a heatwave but the press conference took place in the early morning when the temperature in Berlin was 66F (19C).

A government official said that while Merkel attributed the tremors on June 18 to drinking too little water and too much coffee on a hot day, Thursday's episode was more a psychological issue as she tried desperately to avoid a repeat.

'The memory of the incident last week led to the situation today - so (it was) a psychologically driven process,' the official said. 'There is nothing to worry about.'

Medics have speculated over what caused her to shake, with suggestions ranging from an over-active thyroid to low blood sugar.

Most doctors, however, are in agreement that the shaking is unlikely to have been caused by dehydration or Parkinson's disease.

Peter Garrard, a professor of neurology at St George's, University of London, told MailOnline during the German Chancellor's first shaking episode that her symptoms 'seemed to fit' those of orthostatic tremor - a rare neurological condition that used to be known as 'Shaky Legs Syndrome'.

Today, after seeing footage of her trembling as she met Germany's President, Professor Garrard said orthostatic tremor is still the most likely cause.

Orthostatic tremors often cause people to tremble in one or more parts of their body. This is often worse when they stand, with many sufferers having tell-tale 'shaky' or 'frozen' legs. The problem tends to resolve when they walk, sit or lie down.

Stress can make the shakes worse, which then becomes a vicious cycle as tremors cause the patient to become increasingly uneasy. There is no denying Merkel has a stressful job, however, it is one she has held for 14 years. This led many to dismiss suggestions her shakes may be down to nerves or a panic attack.

The tremors, which can last just a few seconds, can also come on for no apparent reason. The rare disorder tends to strike people in their sixties.

Over time, the condition can cause fatigue, pain and immobility. While there is no cure, drugs like Clonazepam can ease the symptoms.

Walking aids like scooters, sticks or even wheelchairs in extreme cases, may eventually be required. However, only Merkel's arms and hands have been seen shaking to date.

GP Dr Sarah Brewer, a medical director of Healthspan, told MailOnline the shakes could have been brought on by anything from an over-active thyroid to side effects from medication.

One practitioner, Dr Mike Fitzpatrick, said in the wake of her meeting with Zelenskiy that the shaking may be a symptom of an infection.

'Honestly, to me it looks like an infection,' Fitzpatrick said. 'Sometimes when you have an infection, you'll find the body will shake.'

'I read that there'd been some mention of dehydration but I don't think it looks like that to me. You wouldn't normally get shaking like that with dehydration,' he added.

'If you were starving, maybe, but thirst wouldn't do that to you.'

After the ceremony with Steinmeier, Merkel went on to the Bundestag lower house of parliament for the swearing-in of the new justice minister. She showed no signs of shaking and looked relaxed, chatting and laughing with Vice Chancellor Olaf Scholz.

Merkel, who turns 65 next month, was attending a ceremony today to decommission Justice Minister Katarina Barley, who is leaving to become a lawmaker in the European Parliament.

Merkel's spokesman said she would participate later in the swearing in of the new justice minister.

Asked if the chancellor would take part in this weekend's G20 meeting in Japan, the spokesman said: 'Everything is taking place as planned. The chancellor is well.'

She is due to fly to Japan later today although many leaders have already gathered in Osaka this morning.

According to German newspaper Bild, when the Chancellor flies to international summits, she is always accompanied by a doctor and a paramedic from the Ministry of Health's health service.

Fears for Mrs Merkel's health had been sparked just over a week ago when the Chancellor appeared unsteady and shook as she stood in the midday sun next to visiting Ukrainian president Volodymyr Zelensky, whom she was welcoming to her office building in Berlin with military honours.

She was asked by a reporter about her wellbeing at a news conference about 90 minutes later, when she said: 'I've drunk at least three glasses of water and so I'm doing fine.'

Zelensky, 41, made light of Merkel's uneasy spell, joking that he would have come to her rescue if necessary.

'She was standing next to me and completely safe,' he said.

An aide stepped in to offer her a glass of water, suggesting she may have been suffering from the dehydration she claimed caused the last incident of shaking

Merkel had been attending a ceremony on Thursday to decommission Justice Minister Katarina Barley

Members of the German and international media watched on as Merkel struggled to contain the shaking

Mrs Merkel's whole body visibly shook and she pursed her lips as she tried to contain the situation as she stood with Zelenskiy in the 28C (82F) heat while a military band played their national anthems outside the chancellery.

But following the anthems, Mrs Merkel seemed better, walking quickly along the red carpet with Zelenskiy into the building, pausing to greet the military band and taking a salute.

Appearing at a press outing on Wednesday last week Merkel told students during a visit to Goslar in Germany's Harz mountains 'I feel well' after shaking during her meeting with Zelenskiy 24 hours earlier.

Health professionals speculated on the cause of the tremors - with many in agreement that they were unlikely to have been caused by dehydration.

Although Merkel denies there is any cause for concern, one doctor suspects she may be suffering from an orthostatic tremor.

It is not publicly known if Mrs Merkel, who has led Germany since 2005, has any health problems.

German privacy laws are very strict on that type of information being published by the media.

There were brief concerns about her health in 2014 when she was taken ill during a television interview. The broadcast was interrupted when she experienced a drop in blood pressure.

Seibert explained at the time the leader did not feel well for a moment, then ate and drank something and continued the interview.

Merkel is frequently called the European Union's most influential leader and the most powerful woman in the world.

She has said she will leave politics at the end of her current term, in 2021.

Mrs Merkel was seen shaking under the midday sun earlier this month as she welcomed visiting Ukrainian president Volodymyr Zelensky (pictured)

German Chancellor Angela Merkel welcomes Ukrainian President Volodymyr Zelensky upon Zelensky's arrival at the Chancellery ten days ago

Merkel is renowned for her work ethic and has a reputation for outlasting other leaders at European Union summits with her ability to focus on the details of complex discussions deep into the night.

In the past, she has joked that she is a 'sleep camel' who can go days with just a few hours of sleep as long as she gets a full night of shut-eye at the weekend.

Merkel has loomed large on the European stage since 2005, helping guide the EU through the euro zone crisis and opening Germany's doors to migrants fleeing war in the Middle East in 2015 - a move that still divides the bloc and Germany.

Merkel began a stage-managed gradual exit from politics in October, when she said her fourth term as chancellor would be her last and that she would not seek re-election in 2021, when the next federal election is due.

In December, Merkel handed over the chair of her Christian Democratic Union (CDU) to her protege Annegret Kramp-Karrenbauer, though her unconvincing start in the role has set back the party's plans for a smooth leadership transition.

Merkel is well known for enjoying an active and healthy lifestyle - with hillwalking being one of her favourite pursuits.

She and her husband famously take an annual walking holiday in the region of South Tyrol.

Every year since 2008 she and her husband, Prof Joachim Sauer, have stayed at the same four-star hotel in the resort of Sulden.

Last year she cancelled the holiday for the first time in a decade after enduring a punishing year in politics.

In 2018 Merkel narrowly averted the collapse of her coalition government in a row with Bavarian conservatives over immigration and faces a challenge from the far-right Alternative for Germany (AfD).

The German Chancellor, 64, told students on Wednesday last week 'I feel well' during a visit to Goslar in Germany's Harz mountains 24 hours after her meeting with Zelenskiy

Merkel attends the oath of office ceremony for new Justice Minister Christine Lambrecht at the German parliament Bundestag after the press conference today

The chancellor appeared to have recovered from her earlier shakes as she chatted to other German politicians