The reason why you can't move your hand when you wake up is a result of the nerves being compressed and blood flow being restricted to the hands and arms which can lead to numbness and tingling in your hands and arms which is normal and happens to many people.
When we sleep we often unintentionally and unknowingly place our arms and hands in positions that restrict the blood flow and place compression on the nerves such as laying on the arm or hand or having the hand or arm stuck under a pillow or in an uncomfortable position.
It's mostly harmless and goes away soon after you wake up and you should be able to move your arm and hand within 30 minutes or less.
Massaging the hand with your other hand or having someone massage it or trying to move the hand can get the blood flowing again and restore movement to your hand.
The reason why your arms and hands go numb at night is a result of nerve compression and restriction of blood flow.
When you sleep you can unintentionally place pressure on the nerves in your arms or hands and that pressure can compress the nerves and even restrict blood flow and cause your arms or hands to go numb.
The pressure on the wrist or arm impedes blood flow and compresses the nerves and leads to the numbness.
It's usually nothing harmful and the hand numbness and arm numbness should go away within a few minutes or so after you wake up.
You can also move your hand and arms around to help get the blood flowing which can help the numbness in the hand and arms go away sooner.
Sleeping on your arm or hands is most often harmless although in rare cases you can get nerve damage from sleeping on your arm or hand.
However getting nerve damage from sleeping on your arm once in awhile is unlikely to cause any actual nerve damage whether or permanent or temporary.
Sleeping on your arm can cause temporary nerve compression and cause tingling and numbness which is also known as the arm falling asleep and is a normal occurrence and happens to many people.
Most people are just fine after sleeping on their arm the arm numbness often goes away within a few minutes or so of waking up and moving your arm around.
However prolonged or repeated pressure on the nerves and especially your radial nerve can cause more serious issues such as wrist drop.
Your body will also wake you up before any actual damage to your nerves sets in so you should be just fine.
I have an arm falling asleep at least once a week if I roll over on it or have the arm placed under a pillow and often times I'm so asleep that I don't even know I'm in these positions.
When we sleep, we often unintentionally place pressure on the nerves and most commonly the radial nerve.
The radial nerve is a nerve that runs from the armpit to the hand.
The pressure can restrict the blood flow and cause temporary numbness, tingling or a pins and needles sensation which goes away pretty quickly in most cases.
Occasionally placing pressure on your arms and your arm going numb is unlikely to cause any issues but in rare cases it could lead to nerve damage such as Saturday night palsy or honeymoon palsy which can occur when you fall asleep when a nerve is compressed for a long period which can lead to wrist drop.