There's a characteristically brilliant Peanuts strip which opens with Linus sitting on the living room floor, anxiously clutching his mouth. Lucy enters and asks what's wrong. "I'm aware of my tongue," he explains. "It's an awful feeling! Every now and then I become aware that I have a tongue inside my mouth, and then it starts to feel lumped up ... I can't help it ... I can't put it out of my mind ... I keep thinking about where my tongue would be if I weren't thinking about it, and then I can feel it sort of pressing against my teeth."

Loudly declaring this the dumbest thing she's ever heard, Lucy scowls away. But a few steps down the corridor, she stops dead in her tracks. She clutches her own mouth. Suddenly she's aware of her tongue too. She runs back and chases him round the room, shouting, "You blockhead!" with her gigantic booming gob.

Occasionally, late at night, while trying to sleep and failing, I experience something similar - except instead of being aware of my tongue, I'm aware of my entire body, the entire world, and the whole of reality itself. It's like waking from a dream, or a light going on, or a giant "YOU ARE HERE" sign appearing in the sky. The mere fact that I'm actually real and actually breathing suddenly hits me in the head with a thwack. It leaves me giddy. It causes a brief surge of clammy, bubbling anxiety, like the opening stages of a panic attack. The moment soon passes, but while it lasts it's strangely terrifying.

I asked around and discovered to my that relief I'm not the only one. Many of my friends have experienced something similar and have been equally spooked. One of them, a smartarse, pointed out that Jean-Paul Sartre was so rattled by the sensation that he was inspired to write an entire book about existential dread called Nausea, which became a student classic. I prefer Charles M Schulz's take. It's far more succinct and comes with funny pictures.

Anyway, what troubles me about such moments of heightened awareness isn't the dizzying headrush that accompanies them, but the implication that the rest of the time I must be essentially asleep, cruising around on autopilot, scarcely even aware that I'm alive. Here, but not here. Like I'm watching a TV show. That's the bulk of my life. I might as well set the video and nod off completely, catching up later while eating a takeaway dinner.

I didn't mention this to my smartarse friend - but if I had, they'd doubtless point out that Kurt Vonnegut was so rattled by this sensation that he was inspired to write an entire book about it. In his 1997 novel Timequake, a bizarre rift in time sends everyone on Earth back 10 years - but only in spirit. Trapped inside their own heads, mere spectators, they're forced to watch themselves living their day-to-day lives for an entire decade, making the same mistakes, experiencing the same joys and heartaches - and they're powerless to intervene. Naturally, they get bored and drift off, leaving themselves on autopilot. At the moment the timequake eventually ends, and they're back in the present day, most of them simply drop to the floor, confused - it's been so long since they were at the controls, they've forgotten how to walk and talk for themselves.

That's the stuff of science fiction, but it increasingly applies to our everyday lives. The gap between your stupid face and cold hard reality is increasing all the time. We plod down the street holding remote conversations with voices in little plastic boxes. We slump in front of hi-def panels watching processed, graded, synchronised imagery. We wander through made-up online worlds, pausing occasionally to chew the fat with some blue-skinned tit in a jester's hat. We watch time and space collapse on a daily basis. Our world is now running an enhanced, expanded version of reality's vanilla operating system.

As a result, it's all too easy to feel like a viewer of - rather than a participant in - your own life. And living at one remove can be crippling. You spend more time internally criticising your own actions, like a snarky stoner ripping the piss out of a bad movie, than actually knuckling down and doing stuff.

All of which means that those late-night moments of lurching fear, of existential nausea, of basic "I'm alive!" horror now feel more extreme than ever. The gap has widened. Our sleep is deeper. We're like mesmerised rabbits. That explains why we fail to do anything in the face of mounting dangers. We've done piss-all about global warming, the Bush administration, and Piers Morgan's rising media profile - each of which has the potential to destroy us all - because we hardly know we're born.

That's my theory anyway. Clearly, the only solution is for us to set about smashing up every single machine in the world, before we nod off completely. Yeah. That's the best conclusion I can draw at present. Because I didn't set out to write a weird existential column this morning, but hey: I'm fast asleep myself. Sue me when you wake up.

· This week Charlie was too busy to spend more than a few cursory minutes cruising round Liberty City in Grand Theft Auto IV, but was gratified to note that people now go flying through their windscreens when you crash into them at maximum speed: "That's proper progress, that is."