An advanced PT person should be able to do a full evaluation and that might help the drs narrow the possible issues down.

MRI is good for showing what might be a cause or not, but sometimes a hands on evaluation is needed, or even blood work to check deeper to rule out certain other conditions. If you are just starting to track this down I'm sure dr will explore fully. If not seek out another dr.

I you had the hand issues before the MRI, why wasn't a c spine MRI done at the same time?
But if no hand pain only falling asleep? Could be blood flow issues?

What kind of work did you do or do now?
desk work, very repetitive, overhead?
Some of the upper body sx could be related to posture and uses over long time..

Does changing position of legs/feet make any difference when they fall asleep?

My dad had a calcium deposit on his lower spine that would cause his foot to fall asleep and be weaker, once it was cleaned out he has much better mobility.