Shoulders clicking/popping and feel a bit off

Jambalady

I started P90x in the new year and lately my left shoulder has been clicking every time I rotate it. It doesn't hurt, it just feels weird, like it's not sitting right or something, and when I do my workout, it's definitely not as strong and starts to hurt.

Is this something I can stretch or do something about so I can continue to work out? Like I said, there is no pain, just a general "off" feeling in the way it sits and a clicking/popping noise when I rotate it.