Don’t worry! It’s called sleep paralysis and it’s quite common. Kind of the inverse of sleepwalking; instead of moving in your sleep, you’re frozen and awake. Usually accompanied by auditory and visual hallucinations of phantoms or ghosts. Probably the basis of alien abduction stories and earlier tales of faeries and incubi. Read the wiki!
I’ve had what the OP experienced. In the end I found out it was because of some medication I was on. I’ve stopped using it, but I still occassionally have it. It’s not that often anymore, but still happens a few times per year. The feelling is intense. In the middle of the night I wake up from some random dream. Nothing scary was happening at all, and at first upn waking all seems fine. But after a few minutes I experience this most primal fear I’ve ever known. Sweat in my hands, heart pounding, balls retracting up my abdomen. This fight or flight feeling comes over me, but there is nothing to fight and nothing to flee from. This lasts for a few hours and eventually my body tires of the adrenaline and I fall asleep. The next day I amount to nothing and usually take off from work.
The first time this happened I actually drove to the ER because I thought I had a heart attack or something. Since then I’ve learned to llive with it.
You’re right, I should have said “conscious” vivisection.
cmyk’s was pretty awful. The scariest thing I can think of is having some insect or worm injected into my body. If I felt a beetle trapped in my abdomen, squirming around over my organs, I’d probably rip my own torso open with my hands to get it out.