I'm no expert, but I had a similar problem. It wasn't as severe as yours sounds, but It got a lot better after I cleaned the throttle body. The butterfly inside was just a little gunky, and wouldn't close consistently all the way. Didn't make much difference when the car was thouroughly warmed up, but when it was cold it would idle rough. It seemed like it was misfiring on one or two cylinders. It is simple and quick to do. Hope it helps.