I woke up 2 weeks ago and my left shoulder hurt. I couldn't lift my arm more than halfway without the pain becoming almost unbearable. As I lift my arm, it feels tight, like it is going to pop. Eventually after about a week it started to get better and when I lifted my arm I can feel it catching. And then today, I took a nap, and it was so much worse than it ever was. Now the pain is traveling down my arm. Someone please explain what's going on. I never fell, I don't play sports. There's literally no reason for it to hurt.
You probably have an impingement in your shoulder joint....Google it...Shoulder Impingement Syndrome...it is very common...I actually had surgery to relieve it, but there are other things to try first. You may need a diagnosis from an orthopaedic surgeon.