SHoulder Pain
Some people feel it might be the bicep, but I would bet money that it is your rotator cuff, specifically your anterior delt....
Save yourself from rambling. To this test. Take anything from 5-10 pounds and lift it at a 45 degree angle like a front raise. If it hurts, you have a shoulder problem, read on.......
I have the same problem from going heavy on shoulder presses. What I do is light presses and stretches for the first 3 sets.... I do 15, 12, 10, 8, 6, and 3. for each rep I do arnold presses, regular presses and ones with my palms facing in. and then superset with front and lateral raises. what this does it hit the delts from several angles and warms them up nice. Once I get heavy (relative to your strength) I do just regular presses..... After that I do just rotator cuff stuff. Internal and external with cables and one that I think might help you.. A 45 degree front raise. It used to be called dump the can. where you would lift the can and pour.... Just lift 45 and bring it back down. Hope this helps....