Sometimes the arm hurts and sometimes it doesn’t may be caused by prolonged compression, cervical spondylosis, osteoarthritis and other diseases, or other diseases such as bone fracture. 1. Prolonged compression: If the patient presses the arm for a long time while sleeping or working, it will lead to poor blood circulation in the arm, which will lead to the phenomenon of arm pain sometimes and sometimes not. 2. Cervical spondylosis: cervical spondylosis is mainly caused by long-term strain on the cervical vertebrae, osteophytes and other factors, and the main symptoms of patients are neck and back pain, numbness of the upper limbs, pain and other symptoms. In addition, patients with cervical spondylosis will also experience numbness of the lower limbs, weakness of the hands, dizziness and other symptoms. 3. Osteoarthritis: the pathogenesis of osteoarthritis is not clear, and it is considered to be related to age, obesity, inflammation and other factors. Osteoarthritis patients will have intermittent hidden pain, joint stiffness, joint enlargement and bone friction sensation, joint weakness and other symptoms. 4. Other: Fracture, shoulder dislocation and other diseases can also lead to the phenomenon of arm pain sometimes and sometimes not. When the patient has the symptom of arm pain sometimes and sometimes not, it may be caused by prolonged compression and does not need to be treated. If it is caused by diseases, patients should seek medical treatment in time and follow the doctor’s instructions.