Personal experience: If I fall asleep in a number of different postures, I also experience numbness, as I have since I was about your age. If I fold my arms, kink my wrists, place my hands under my head, etc, numbness typically ensues. Depending on which nerves are pinched off, the thumb and adjacent fingers may be numb, the pinky and adjacent fingers may be numb, or they may all be. If I fall asleep on a hard wooden chair, my legs may be numb and I may be unable to walk in a controlled manner when I extract myself from the silly thing.
Research: Unless you do have a disorder, deficiency, or tendency to use mind-altering substances, you will probably have no long-lasting effects from this phenomenon. According to James Dyck, MD, it could be you are actually waking up before your body is. I quote, “...During REM sleep, the brain sends a signal to cause a body-wide paralysis. The purpose of this is to keep you from acting out dreams (which occur during REM). But if you wake up during one of these phases, you can be conscious before your [sic] fully regain control of your limbs. This is called sleep paralysis, and it can be a frightening situation. You're stuck somewhere in between dreaming and wakefulness, and you can't move...”
What seems to me is happening is a little different, he explains what seems to be your condition (and mine) like, “The nerve compression has led to a temporary paralysis (perhaps because you got stuck in a compressed position during REM).” He warns, “Compressing nerves can damage them. The good thing is that the body will naturally wake up as a protection mechanism when a nerve has been compressed too long. After you wake and relieve the pressure, the nerves will quickly come back online, usually first with a pins-and-needles feeling.”
I recommend reading this article in full:
If your consciousness is impaired, eg, from alcohol or drug use, you may not wake up until you have already caused at least temporary damage to your nerves.
It is possible that a deficiency or disorder is causing the numbness*, so it is recommended to see a physician if numbness or tingling persists,** and I would say the same would go for weakness, particularly if it’s at all possible to be certain that you aren’t imagining yourself to be weaker. Are you measurably unable to lift or reposition the same items or weights you used to?
If you’ve ruled out disorders, or possibly in diagnosing whether it’s normal or something to be concerned about, you can try the following list of remedies from lovetoknow.com:***
“To reduce or prevent this from happening, try the following tips:
Keep your hands from being under a pillow or your head while you sleep.
Don't lie directly on your arm and cut off the circulation.
Don't fall asleep with your hands in a fist; try to keep them uncurled.
Hold your hands above your heart to help them "wake up."
Try drinking ginger tea, which can improve circulation.
Try doing exercises to strengthen your shoulders, neck, and arms.
Try using softer pillows, including a knee pillow, and sleeping on your back (side sleeping can cause hands to fall asleep when they're under the pillow).
If you're having carpal tunnel or tendonitis problems that are causing your hands to fall asleep or feel numb, an anti-inflammatory drug might also be helpful.
Nocturnal support braces for your wrists and hands can help reduce the tingling sensation that disrupts your sleep. Splints can provide support, help you avoid bending the hands and wrists awkwardly and reduce the chance of crimping any nerves.”
I personally would recommend trying some braces that keep your wrists from bending freely. If that doesn’t help, it could be that keeping your elbows straight will fix the problem. Either way, the advice will always be to consult with your physician, which makes a lot of sense if he knows any more about you than you’ve described, especially if he has experience in the field. Hope this helps.