Carpal Tunnel Syndrome: This condition is the most likely cause of intermittent numbness in the hands, particularly in the thumb, index, and middle fingers. It occurs when the median nerve is compressed at the wrist, often due to repetitive motion or fluid retention.

Ulnar Nerve Entrapment: Compression of the ulnar nerve at the elbow or wrist can cause numbness and tingling in the ring and little fingers.
Radial Nerve Compression: Compression of the radial nerve can cause numbness on the back of the hand or the thumb side of the hand.
Thoracic Outlet Syndrome: Compression of the nerves and/or blood vessels that pass into the arm can cause numbness, tingling, and weakness in the hands.
Peripheral Neuropathy: Damage to the peripheral nerves can cause numbness, tingling, and weakness in the hands, often due to diabetes, vitamin deficiencies, or alcohol abuse.

Multiple Sclerosis: A demyelinating disease that can cause numbness, tingling, and weakness in the hands, as well as other neurological symptoms.
Stroke or Transient Ischemic Attack (TIA): Sudden numbness or tingling in the hands can be a sign of a stroke or TIA, which requires immediate medical attention.
Cervical Spine Disease: Herniated discs, spinal stenosis, or other cervical spine conditions can cause numbness, tingling, and weakness in the hands.
Vitamin B12 Deficiency: A deficiency in vitamin B12 can cause numbness, tingling, and weakness in the hands, as well as other neurological symptoms.

Guillain-Barré Syndrome: A rare autoimmune disorder that can cause numbness, tingling, and weakness in the hands, as well as other neurological symptoms.
Lyme Disease: A bacterial infection that can cause numbness, tingling, and weakness in the hands, as well as other neurological symptoms.
Sarcoidosis: A rare inflammatory disease that can cause numbness, tingling, and weakness in the hands, as well as other neurological symptoms.
Tumors: Rarely, numbness in the hands can be caused by a tumor compressing a nerve or affecting the spinal cord.