The shoulder pain could simply be a lack of sufficient warmup. Before I even hit the bench I've typically done 30-60 reps each of facepulls or band pullaparts and hammercurls or another curl variation to push blood in my shoulder. Typically 2-3 sets with the bar, then 95, then 135 and so on making divided jumps to my work weight for the day. All of this often after I've drug the 100lb sled several hundred feet fwd and backwards, or some other GPP movement to raise my heartrate and body temp.
This only takes 15 minutes tops and prepares my body to train flat out as safely as possible.