@Bill Bauer It lasted probably 15 seconds for me. I panicked when I couldn't move my arms and just fought to move something, felt like I was sinking into death. I didn't see anything, but I did hear a flurry of whooshing noises that increased as I fell back into sleep and went away as I fought to wake up completely.
I used to get it all the time. I would force myself to relax, and not try to move. Then it would wear off quite quickly.
It happens because the mechanism that makes us immobile during sleep so we don't act out our dreams hasn't worn off at the same time as us waking up. So although we are awake, we are still immobile as though we are asleep.
It happened to me once when I was 16-17 (now I'm 33). I woke up and could not move a muscle, I could only think about it, plus I could not breath properly. It lasted 10 seconds or so. Also I remember that my eyes were open and I saw my room but, at the same time, my dream continued. It was very weird. Actually, maybe it happened couple of times, I just don't remember.
I haven't experienced it in a good long time, but woke up to it quite a lot when I was younger and it used to freak me out because it always when hand in hand with the feeling of somebody choking me or a weight being placed on my chest so I wasn't able to breathe properly. Nasty shit!
Experienced it twice. Once upon waking, I hallucinated a blue demon sitting on my chest, spitting hornets at my face lol. And one other time, when I was falling asleep at night. Could not move for several minutes while still awake. Freaked me out. No hallucinations that time, though.