My left hand suddenly got really numb, though I don't use it much. It began recently with both hands too. & I've been using computers and mobile less?

Carpal Tunnel. Your symptoms suggest bilateral Carpal Tunnel Syndrome, which can be triggered by Typing/Keyboard use. CTS can also be related to hypothyroidism, so see your Physician for an evaluation and blood tests. Most people will respond to NSAID treatment and wearing wrist splints at night, but prolonged CTS will need evaluation by a Orthopedic Surgeon.