does it feel like the handbrake is being pulled on and off? and you have to really floor it before it'll do anything? otherwise it sort of grumbles and shudders? mines been doing this. it was a wire into the alternator, now the problems returning again though. im wondering if its a failing O2 sensor (maybe a bad earth) or fuel pump. mine does it from cold and sometimes when its run for a good while as well. im stumped. it was really violent jerking, this was sorted by a polyurethane front mount as the OE was almost non-existant due to wearing out. but the problems still there.