I just started lifting again about 3 weeks ago, and I've been going at it pretty hard, but now it seems I have a problem that may end it all again. Everytime I do bench and incline, my left shoulder just goes weak. It's a bigger problem on incline than bench, but it's weird because it doesn't really give me any problems any time that it isn't loaded with weight, but it just goes out on me without much warning. Anybody have any idea what it might be?