I suffer with the same problem, almost every night I wake up with pins and needles or numbness in my left hand, mentioned to my doctor who didn't seem concerned and said it was proberbly a mild form of carpal tunnel syndrome.
Try to sit on a high table without your leg torching the ground. For some minutes do not wear shoe and watch out if it is the same feeling in you hand which normally wakes you up, then you will know its blood circulation problem. Take iron supplement on a daily bases.
Do you sleep with your arms bent? That stops the circulation to your hands. Also, it could be a poor circulation problem - might want to try taking a cod liver oil supplement and CoQ10 to give your heart a break. Hope it helps.