1) Your shoulders may just be tight and the overhead position may just irritate the shoulder girdle a little bit. If the pain goes away within minutes after doing overhead presses and jerks then I wouldn't think there's anything to worry about. This sport is tough on the shoulders.
2) I would definitely continue to do your dynamic shoulder warm-up. Also try to work in some stability exercises. KB Arm Bar, KB Bent Press, whatever else you can find (I'm sure there's a million of them).
If that doesn't help and this continues to get worse, then I recommend going to a PT to get it professionally evaluated.