I Have Occasional Sharp Pain (pinched Nerve??) Just Under My

I have occasional sharp pain (pinched nerve??) just under my clavicle near my left shoulder. I might be reaching up for something or just moving in a certain way and all of a sudden it is an extremely sharp stab that goes away within seconds. I can do the same movement that brought it on minutes later and no pain. I am a 63 yr old female in otherwise good
health. What might this be?