Loss of control in my arm upon awakening, intense.

This has happened to me before but this morning was particularly weird.
Anyway being a guy I stayed up way too late so when I finally went to bed I fell asleep in seconds.
But when I woke up my arm was numb, probably just from sleeping on it wrong, and my fingers hurt. I sat up quickly to see what was wrong with my arm and I tried to move it, but it just started flailing about seemingly all on its own and slapped me in the face. After a short time I got it working properly I wasn’t too freaked out because this has happened to me before. Once with the flailing and another time where my arm was totally numb and unresponsive for a good 5 minutes I had to beat it to death to get it working again. No big deal I guess I feel fine.
However, I keep a knife on my box spring between my mattress and the headboard just in case I should ever need it. We’ve been robbed before.
But this morning I noticed a stinging scratch on the knuckle of my thumb.
How the hell could I possibly have reached my hand down in between the mattress and head board while sleeping and cut the top of my thumb of all places in the process. In order for that to happen I would have had to be laying like sideways and have my arm twisted backwards or something.

Anyway I’m not too worried about it, but I thought I’d share my really effed up morning with you all haha.

That would be awesome. I wish my arm would randomly slap me in the face lol. Maybe see a doctor about it?