It must be going around. My left shoulder grinds and pops when I rotate my arm. No injury, I just woke up that way one morning. I am slide sleeper. I'll let my Chiro work on it. She'll get it back into shape.
I'm a side sleeper also and started having shoulder problems. I sleep with 2 pillows one for my head and the other I tuck it under my arm pit to take some weight off my shoulder. Works good.