I would guess the idle control valve and the fuel filter. The idle control valve looks like a aluminum cylinder and it's located under the air filter. You have to remove the air filter housing to get access to it It also has two rubber hoses connected to it. After disconnecting the hoses take it out and drench the inside with a carb cleaner several times to clean it.

The next item is the fuel filter. If it's not been changed for a while it's probably clogged and the engine is starving for fuel. On my 300E it's located under the car (near rear side left wheel). You have to remove the cover under the car to change it.

Hope this helps.