It is numb vs being "asleep"? nerve or blood flow?

My arms would go to sleep and I couldn't move them if I happened to sleep with arms over head or folded under the pillow..
Mine was more of a blood flow cut off issue..vs a nerve issue.
I could tell it was blood flow related for me due to the pins & needles sensation when circulation was restored..

My forearms/elbows were hyper sensitive early on , I had to pad/wrap them so they didn't rub or have pressure from the mattress..