Your circulatory system has arteries that carry blood to all parts of the body and veins that carry it back. Arteries are pressurized by the heart but veins don't have any pressure on them. They work through contracting muscles which squeezes the blood out of them to send them back to the heart.

This is why walking is less tiring than standing in one place. In walking you contract the muscles in your legs, which pumps the blood back up to your heart. This means the heart can send more oxygenated blood to the legs.

When you wake up, you stretch all your limbs to squeeze out all the blood (that's not an elegant way to put it, but its the best way I know to describe it). If it's quiet, you can hear a 'drumming' noise in your head. That's the sound of the excess blood being squeezed out of your limbs, stimulating the circulation throughout your body.