There may be the following reasons for shoulder pain after waking up: 1. The most common reason that can lead to this condition is the cold stimulation of the shoulder joint. The shoulder joint is a very flexible joint with a large range of motion because the joint is relatively shallow and surrounded by many ligaments, fascia, muscles and other soft tissues that connect to make the shoulder joint move freely. Therefore, a joint structure like the shoulder joint, which has a complex distribution of soft tissues, can be easily stimulated by cold, which can lead to acute aseptic inflammation of the local soft tissues or impaired local blood circulation, especially during sleep, when you are not careful and get cold. And the pain symptoms that occur after waking up are much less likely to be shoulder joint injuries. 2. If you are a patient with cervical spondylosis, cervical spine hyperplasia has a slight compression of the cervical nerve, and once the sleeping position is problematic or the pillow height is not appropriate, it will lead to increased nerve irritation symptoms and trigger pain symptoms in the shoulder or even the arm.