First, when sleeping, people sleep on their side with their shoulders on the pillow, which will cause your head to press on your shoulders when you sleep. After a long time, the blood circulation in the shoulders will be inhibited and the muscles will not be stretched, so you will feel sore when you wake up.
Second, when you sleep, the quilt is not covered properly, and your shoulders are frozen. When you wake up, you will feel sore.
I have experienced both situations, hehe, if it is the first one, it may be caused by your sleeping habits. Pay attention to your sleeping posture, and you can rub and massage more during the day. If it is the second case, hot compress, cupping and other drug treatments can be carried out. It is recommended to wear pajamas with shoulders when sleeping to prevent catching cold.