Suggest Treatment For Pain In The Arm While Lifting Up

At least once every two months I lose the ability to lift one of my arms. Last time it was my right arm. This time it s my left. The pain starts in the muscle of the upper arms near the shoulder but my shoulder itself doesn t hurt. The pain extends down the muscle almost to the elbow. My elbow doesn t hurt. I can bend my arm fine at the elbow. But I cannot lift my arm at all at the shoulder. This has been happening for over a year.