It can come on quickly. I'm at over 30 years experience now and once, about 11 years ago, my shoulder just started having this shooting pain almost immediately

It can come on quickly. I'm at over 30 years experience now and once, about 11 years ago, my shoulder just started having this shooting pain almost immediately whenever I sat in typing/mousing position. It was kind of terrifying. At times, it was so bad that I legitimately thought that I might have to give up sitting at a computer. I ended up investing in a better chair, focusing on better posture, taking breaks, doing exercises, and also switching my mouse to the left side for about 6 months (the pain was in my right shoulder and was particularly bad in the mouse position, so I thought learning to left-mouse would be a good idea). Ultimately, it worked out, but I had to make some pretty serious changes to make that happen, and now that I'm in the better habits, I wish I'd made the change much earlier.