with 93 400E

[celcius]

I have a 93 Mercedes 400E that was running great until recently. For the past month, the car shakes a little in idle and hesitates when the accelerator is pressed--no matter how far the accelerator is pushed, the rpm's only go up a little without an increase in speed; then after a few seconds, there is abrupt acceleration. When the car goes at a constant speed, the drive is smooth; but as soon as the accelerator is pushed, the same hesitation problem happens.

The weird part is that if the car is turned off then restarted, everything works PERFECTLY even when the engine is still cold... after starting the car for the second time, the car idles at the same rpms but there is no shaking at idle and no hesitation.

Any thoughts?