Hello guys I've recently bought a Mercedes W221 S600 V12 twin turbo. I noticed that when the car is idling I feel the car shaking a little bit. The revs don't drop at all and when you rev the car slow or fast the engine is actually very smooth... there is no hesitation. After driving the car for about 30 mins to 45 mins then the car is very smith on idle, the shaking goes away There are no warning lights on. It says it's not due a service for quite some time but I will get the service done anyways. Could it be the spark plugs? If anyone has come across this issue before please let me know Any info/advise is much appreciated!