Hi, Thanks for writing in. The main blood vessels supplying the back of the head passes through between the small bones of the neck. The nerves supplying the arms also originate at the cervical portion of spinal cord in the neck region. These pass through small foramen in the cervical spine and then reach the arm. Sudden compression of the blood supply causes blackout and pinching of the nerve at its origin or anywhere along its route can cause numbness, tingling sensation as described by you. Since it is happening for last 2 or 3 years then you need to consult a neurologist and get examined in detail. Another possibility is a a partial complex seizure and this requires complete clinical examination, electroencephalography and imaging scans.