Mine goes a bit deeper. My arms fall asleep to teh point of pain and swelling.
We found that when my BG goes way down circulatrion also goes down.
Another event is a dislocated or pinched nerve.

My husbadn had cubital tunnel from a compressed C4.5 and 6 nerve in his neck that caused his same sensation.

I think its part of old age and " settling" but you never know. your bed could be causing a lseep position that put pressure on your nerves.

Sleep in an ew position and if it doent happen all the time, make a mental note fo when it DOESNT happen and what you did that day or night.
a little detective work might uncover the mystery........