Both arms and legs especially arms get numb only when I wake up and only for a while and I have no pain. I told doc to send me for a brain and cervical spine MRI and everything was fine. What is it?

Weird. If MRI is normal, then suggest getting flexion/extension x-rays of the cervical spine as their might be abnormal movement of your neck causing some slight stenosis in your neck. Also consider spine specialist if no relief. Often MRI is not read correctly by radiologists so having specialist look at it.
Peripheral nerve. At least regarding arms, you might possess mild early nerve compression at wrist c/w carpal tunnel syndrome. Regarding legs, might wonder about low level peripheral neuropathy. An EMG study of a few nerves in arms and legs could fully clarify lingering questions.