I just purchased this car which has 60K miles. Cold ignition & idle seem normal, but during the first few minutes, the car hesitates when I try to accelerate from a stand-still (not hard acceleration, just normal city driving). It doesn't stall; the pick-up just seems to be a couple of seconds late. This is quite dangerous when it happens at an intersection. But once the car is warmed up, the problem is gone. What is likely at fault? Thanks.