Physiologically, sleep paralysis is closely related to the paralysis that occurs as a natural part of REM (rapid eye movement) sleep, which is known as REM atonia. Sleep paralysis occurs when the brain awakes from a REM state, but the body paralysis persists. This leaves the person fully conscious, but unable to move. The paralysis can last from several seconds to several minutes "after which the individual may experience panic symptoms and the realization that the distorted perceptions were false". As the correlation with REM sleep suggests, the paralysis is not entirely complete; use of EOG traces shows that eye movement can be instigated during such episodes. When there is an absence of narcolepsy, sleep paralysis is referred to as isolated sleep paralysis (ISP).
It happens all the time to me, and it scares the hell out of me. I'm awake, but I can't move, and I have to literally think about throwing my body up to get out of it. When I finally regain control of my body, I jerk really badly.
Anyway, I was just wondering if this happens to anyone else?