Shoulder pain is not something I have experienced----Except for a Frozen Shoulder. It used to catch me if I kept my shoulder at a certain position and angle for a certain amount of time.

Luckily - after the first set of treatment I knew how to cure it without 6 weeks of Physio and time off work.

So even if it is not Frozen shoulder- You may have the hand/ bar position set up wrong. No easy way to check this out- but raise or lower the bars and see if the shoulder is still affected. See if your LBS can suggest a different ride position- Try raising the saddle-

Try anything to try and eliminate the pain. If you can't----- get to the quacks and get it checked out.