The left hand middle finger involuntarily moves by itself, considering the cervical spondylosis compression of the nerve, too much local activity leading to joint muscle strain, excessive alcohol consumption to stimulate the cerebral nerves and other reasons. 1. Cervical spondylosis: cervical spondylosis is a disease of cervical intervertebral disc compression of peripheral nerves or spinal cord due to long-term improper sitting posture, external forces, degenerative lesions and other factors, compression of the nerve root can cause abnormal sensation of the skin innervated by the nerves, muscle movement abnormalities, etc., and involuntary movement of the middle finger of the left hand, numbness, hypesthesia, and other symptoms. 2. Chronic strain injury: chronic injury of muscles and ligaments caused by long-term use of the middle finger of the left hand and improper exertion can lead to involuntary movement of the muscles of the middle finger of the left hand, accompanied by pain, swelling and other symptoms. 3. Alcohol stimulates brain nerves: long-term alcohol consumption can stimulate brain nerves and lead to personality and cognitive changes, alcoholic dementia, involuntary muscle movement and other symptoms. There are many reasons for the involuntary movement of the middle finger of the left hand, it is recommended to consult a doctor for a clear diagnosis and targeted treatment under the guidance of the doctor.