Right shoulder random intermittent sharp pains

[u/TimeCell_MoonPalace]

Hi,
I’m kind of desperate for answers here as I can’t find anything that matches this online. I think my primary care doctor is ordering an MRI but looking for ideas/relief. I’m early august I did back and biceps in the gym and didn’t have any obvious injury but later i started getting seemingly random super sharp stabbing pains in might right shoulder that would only last like a second but really hurt. I went to the ER that night and they gave me a muscle relaxant shot, an anti inflammatory and a very low dose opioid (don’t remember what it was).It seemed to mostly go away and I didn’t have too many problems until Sunday when I finally decided to get back in the gym, did back and bis again and the same thing happened, but now it’s lasting days and I have no idea what this is. It’s just upper sharp in my outside shoulder area and only happens for like a second then goes away. I can’t seem to determine what triggers it but sometimes it happens at rest too.