For a few years now i have been getting a sudden shoulder pain that causes a bit of numbness in my arm(always left side) that usually goes away within a few hours or i'll go to bed with it and wake up in the morning and its gone. The pain only happens every 2-6 months and i'm not doing any strenuous activity or heavy lifting to cause it. It started up again last night and did not go away by morning, seems to be getting better, but has not completely gone away like usual. I'm staring to get a bit concerned about it. Any ideas of what it could be?