Possible reasons for sleeping with a stiff and tight neck include getting cold, neck and shoulder muscle strain, acute neck injury, cervical spondylosis, and so on. 1. Cold: It may be that the muscle tissue becomes tense and stiff due to cold in the neck, resulting in a stiff and tense neck while sleeping. 2. Neck and shoulder muscle strain: it may be due to keeping a posture for a long time, such as working with the head down or often probing the shoulder, which will lead to strain on the neck and shoulder muscles, resulting in muscle tension, spasm, and the phenomenon of sleeping with a stiff and tense neck. 3. Acute neck injury: may be due to the neck movement caused by strains, sprains and other acute injuries, resulting in local muscle tension, spasm state, can also trigger sleep stiff neck tightness. 4. cervical spondylosis: may be due to cervical spondylosis compression to the local nerve root, will lead to the neck muscle spasm, tension state, thus appearing neck sleep stiff and tense situation. Sleeping stiff neck tightness may also have other reasons, it is recommended to go to the regular hospital in a timely manner, improve the relevant examination, clear cause, under the guidance of the doctor for targeted treatment or treatment.