Electrical problem

Hi, I don't know exactly what's going on. I recently got a new stereo installed, and now my car won't start sometimes. I've unplugged the stereo and it still sometimes doesn't start. When the car won't start, it sounds like it is about to start, but never starts. Then the dash light all go on and off and makes noises. I've been trying to try different things to find out the problem. I tried unplugging the antenna cable, and most of the time it works with it unplugged, but sometimes it doesn't. I don't know if that has anything to do with it though. Anyway, when the car does start and I drive it, it sometimes just shuts off which got kind of dangerous today on the freeway. Does anyone have any ideas as to what the problem could be? I brought it to a shop yesterday and they got it started, but then it started doing it again. I'll probably bring it back there, but if I can find a possible answer I'd rather save some money. Thanks a lot.