Erratic idle revs
 

Hi guys! I'm driving a 2012 Mercedes Benz C250 CDi automatic. Recently I've noticed erratic needle movements on idle (to a lesser extent). It does not occur frequently but when it does I can feel the vehicle shaking. It can be annoying when it does happen. What could be the reason for this? I took in to the dealership and at first they could not pick up the problem via the diagnostics. I took the vehicle in three times for the same problem and eventually they told me that I need to change all of the injectors, MAF and fuel filter (at only 110 000 km's?). I am not convinced about this as the vehicle does not smoke, neither does it jerk or lose power.