I didn't read all replies, but from what ABM said, it's like your mind "wakes up" but the body is still "sleeping" and since the mind usually "locks" the body to prevent movement while sleeping, you can't move until your BODY wakes up too?
Damn.
Imagine if the mind gets STUCK in the "awake state" but the body doesn't wake up at all. FUUUUUUUUUCk.
I don't have this... but I do have a strange problem where I'll sleep on my arm wrong, wake up in the middle of the night and have a virtually dead arm (it's so numb). I'll pick it up and drop it and it's kind of fun but at the same time it feels really bad! Eventually it will slowly wake up and I can move it again and all is well (I promptly go back to sleep).
I had this like, last week! I woke up, wanted to scratch my head, and I was like, WTF?? I can't move my arm!! OH FUCK! I pinched it and stuff, nothing, not a single feeling. Then after a while it came back, so I scratched my head and promptly went back to sleep.