It sounds like you should be evaluated by a Board-Certified Fellowship-Trained Hand surgeon.
I'd be happy to see you.
please call 413-582-2600 to make an appointment.

Most commonly it is from carpal tunnel syndrome. If you have neck problems, it may be a combination of pinched nerve in the neck and/or carpal tunnel syndrome. You should get electrodiagnostic studies done which will help in a correct diagnosis.

An entrapment type neuropathy. It can be either a distal entrapment mono-neuropathy like carpal tunnel syndrome, or a proximal nerve root entrapment, aka a radiculopathy. Go see a PM&R specialist specialist.

There are many reasons why your hand goes numb, but the most common is carpal tunnel syndrome. Carpal tunnel syndrome usually causes numbness and tingling at night and during activities such as driving, holding a book, etc. I suggest you see a hand surgeon to get a correct diagnosis.

Hand numbness can be cause by a nerve in the wrist, elbow or neck. I would need more information to determine from where. Numbness is something you want to fix before it becomes permanent.

It is recommended that severe symptoms should be promptly evaluated by a physician with top possibilities being cervical radiculopathy vs. carpal tunnel syndrome, although the onset is not typical for carpal tunnel syndrome. Other possibilities exist, and it would be useful to know if it is just one hand vs. both.

Several things could be going on. Is it the entire hand or part? One (part) candidates indicate nerve damage. The other (whole) could be circulation. I suggest talking to your primary and getting further evaluations and referrals to the appropriate doctor to confirm and treat the problem.