Mine do this periodically, but I usually don't feel it until after a set--sometimes during though. First thing, start working your rear deltoid more (unless you already do extensively). I'll tell you how I warm up for bench press:
1.First I do one set of 135 for usually 5 reps: this is nice and slow and easy for me. Adjust for your strength/weight.
2. Go to the bands and do "light" sets of interior/exterior rotator work. This just warms them up.
3. I just started doing about 10 push ups after the band work.
4. Start with warm up sets working up to working weight. My warm up sets are usually 2-3 reps. The reps drop to 1 when getting close. I usually jump about 25-40 lbs each set. This keeps you from wearing out, but it lets you fire up the CNS.
Keep in mind that this works for ME. It might not be perfect for you. Also, the bench press is my first upper bdy movement, so I'm usually cold. That is why I warm up the shoulders so much. I hope this helps you. And like I said, WORK THE REAR DELTS!