Sleep paralysis

I'm usually not one to try to find rational explanations for things that seem paranormal or otherwise, but I cam across a discussion today that shed some light on something that's happened to me a lot. Now, I have a name for it: sleep paralysis. Like other symptoms, I had no idea it was Chiari related. (Clarification: for me it's probably Chiari related. Other people can have it, too.)

So heres the scenario...

I'm lying there in bed and am half awake, half asleep. Only, I can't move. I'm aware of everything that's going on around me but my body is breathing regularly, like I'm asleep, and my eyes are closed. It's a totally terrifying feeling. Sometimes, it will feel like my body is floating up towards the ceiling.

I thought I had just perfected astral projection. But, apparently, it is sleep paralysis.

Here is your link for more information on the topic: http://www.webmd.com/sleep-disorders/guide/sleep-paralysis

So why does this happen? More symptoms having to do with the blocked flow and crowding in the brain. It's amazing what all that stuff is causing.

It's apparently not dangerous or anything, although I am usually hit with a severe headache when I come out of it. Not that the headache is anything new, though.