My 96 Honda Accord is vibrating really violently having some problems staying on when I'm at stoplights, when I first start it up, stuff like that. Usually in the summer when I have the AC on it does this, so I try really hard to just roll the windows down and avoid using the air. Its winter now, and last night I was driving and I had to stop at a light, and it started vibrating really, really hard, and acted like it was having trouble staying on. It wouldn't stop until I held the brake down with my left foot and rested my right against the gas pedal. Help?