the motor not running well but after restarting it the problem gone. on 1994 Mercedes-Benz SL500

hello there i don't know what to say but i have a serious problem and no one can give me the answer problem is that sometime my car start to shake(vibrate) smoothly when it is not moving like when you have problem in the sparking but when i restart it this shaking gone .

No one will be able to answer your question , other than with a guess , until you can duplicate the symptom AT a shop.
thanks for your concern actually i am so confused and i dont know what to do .