shoulder pinch but only when arm at low angle

Hello Friends,
I have been working out at a gym regularly for almost a year now. I have worked on shoulders off and on and at times i get a pain here or there. But this one pinch is what i wish to be advised about. if i lie down straight with my arms on the floor beside my waist and then try to raise my arms i feel a pinch kind of pain when the arms reach about 25 degree angle. sometimes if i feel muscles pinch when i internally rotate my arm while reclining back with laptop on my lap(like when i type without resting my hands on the laptop).The pinch sometimes is more on the left shoulder. There is no problem when i raise my arms above the shoulder level. its only when the upper arm is low,(the hands might be raised) and especially when the arm/shoulder is internally rotated(elbows going out and away from the body while keeping the hands fixed in front).Since this is present in both my shoulders i am afraid that this might be something permanent in my shoulders like some acrimonial something being wrong. I would be grateful for any light on the subject and a possible solution.
Additionally i would like to know, should i workout my shoulders?