Hi lynny, I have and still have shoulder pain in my right shoulder mostly. It felt exactly the way you describe it. catches on something. Very hot, sore, and frustrating. I was dx with fibro and rhuemitoid arthritis. I believe my doc said that was arthritis in my shoulder. Although my hip feels the same and he said that may be bursitis. So it is some kind of itis. (inflamation)
OH, I am on Prednisone, since then the pain is much better. Too bad it's not good for the bones.
Good luck with your dx. Hope it's nothing too serious. Laura