The possible causes of sudden neck and shoulder pain include inappropriate sleeping position, strain injury of the neck and shoulder, and nerve root cervical spondylosis. 1. Inappropriate sleeping position: It may be related to inappropriate sleeping position. Muscle spasm is caused by too high or too low sleeping pillows, cold neck, etc. Neck and shoulder pain and partial limitation of activities suddenly appear when waking up in the morning. 2. Neck and shoulder strain injury: It may be a strain injury in the neck and shoulder area. Due to excessive stress on the shoulder and neck area, it triggers damage to the muscles, ligaments, fascia, etc., resulting in edema and the sudden appearance of neck and shoulder pain. 3. Nerve root cervical spondylosis: It may be caused by nerve root cervical spondylosis. If the nerve roots in the cervical spine are stimulated, the patient will experience sudden neck and shoulder pain. Sudden neck and shoulder pain may also have other causes, if the pain is not relieved or gradually aggravated, it is recommended to go to the regular hospital in time to improve the relevant examination, to clarify the cause of the disease, and then under the guidance of the doctor to carry out targeted treatment or therapy.