I had an issue with this several months ago. Sleeping in the same position and I would wake up with a dead arm/hand. Always from the hand that I would curl up under my head/pillow. The weird thing was that I had been sleeping in that same position for my entire life.

It really bugged me, and so I tried to force myself to sleep on my back, but I can't do that.

After awhile it went away and I never really figured out what it was... (not saying you shouldn't get it checked by the doc though if it worries you)

K.