And a stiff neck often seems to linger on and on. Most often, a stiff neck is caused by strain on the soft tissues of your neck, but it can be a symptom of many problems and shouldn’t be ignored. Causes of Stiff Neck. A stiff neck may be the result of: Injury. If you had an accident that caused your head to jerk around violently, you may have injured the muscles and perhaps the ligaments in your neck, which can lead to stiffness.