First, saying that the w124 is Chinese to you is blasphemy and should never even be used in the same sentence. Second, have you tested for vacuum leaks? That's where I would start. Then I would check the integrity of the plugs, wires, cap, and rotor: visually making sure they look ok. Next I would move on to check the fuel delivery. My guess would be vacuum though because if it starts fine and runs fine while driving then I don't see it being ignition or fuel, but I have been wrong before.

__________________

1990 190E 3.0L