Memfis

How do you get out of there?

Purposefully thinking of something else, focusing all your attention on that.

Sodaholic said:

I have no idea why that happened or what was really going on, but it still scared the shit out of me when it happened.

There's some sort of chemical that your brain uses to paralyze your body during sleep. Sleepwalkers suffer from a lack of this chemical. You simply woke up before this chemical dissipated.

You were probably on your back the whole time, and you merely dreamed that you rolled over. This chemical doesn't really cause weakness; it works more like an on/off switch.

AndrewB said:

There's some sort of chemical that your brain uses to paralyze your body during sleep.

I think you may have things slightly backwards. The current scientific consensus (always subject to change) seems to be that REM atonia occurs because the release of certain neurotransmitters is blocked during REM sleep, resulting in motor neuron inhibition.

The relationship between REM atonia and sleep paralysis is an unsettled issue, though.