Rough Idle
 

My Mercedes Benz 2003 C-240 with 103K runs good but when engine gets hot it start to have a rough idle. It behave similar to a misfiring engine.
It is very noticeable when stooping at traffic light.
Please give any idea in where in the engine the problem can be.
Thanks

Ignition, fuel, or air/vacuum. Start by narrowing the problem down by ruling out components in those 3 categories.

Maybe your Crank Position Sensor

Assuming all maintenance items are up-to-date and your engine mounts are good, ignition wires are a very common cause of rough idle/misfire.

+1, with the following caveat.

If your engine mounts haven't been replaced and you only notice this at idle in gear (it's fine in park or neutral), then you need to first replace the engine mounts.

Good luck.