Engine breaking up on Mercedes 1993 E220 when slowing down
 

Hi
I have a 1993 Mercedes, E220 Automatic transmission.
I don't know how to describe exactly the problem, but what happens is that when i'm in relatively high speed, and I slow down suddenly for a traffic light, or traffic jam, the engine starts breaking up. The engine does not turn off, but when I stop completely and put the gear to N, the engine gets back to normal.

Any idea what might be causing this? I hope it's not a serious probloem :confused:
I use unleaded fuel.

Maybe I mis-used the word to describe the symptom. What I meant by breaking up is that the car starts shaking as IF the fuel supply is not enough, and as if the engine is going to stop.