I bought a 2015 S600 55k miles. On cold Start CEL come on or get flashly sometime with P0310 and car st idle start to have vibration and shake. Drive it for a minute or so to warm it up and then i shut it off and restart and all will fine no shaking or vibration and eventually the engine check light goes off or i erase.
I took it to mechanic and went on long and costly fix but still the problem hasn't fix yet.
Any ideas, advice on what else should I try!
Here's a list of things i changed
First i replaced all spark plugs no difference same problem
Then, replaced coils numbers #9&#10
After that, replaced injectors #9&#10
Still no difference still same problem
I updated the engine control unit and still no luck
At last, i replaced the engine control unit but again no luck and the problem is atill the same
All parts i replaced are genuine mercedes spare parts
The mechanic have done a compression test for all cylinders but it turns all fine and also tested for any vacuum leak again all tests were fine
My mechanic gave up and has no solution to go with
Any help or any one had experienced the same and got their car fixed!!
Appreciate any help, thanks in advance

 

This is more likely to be in the ignition side of things than elsewhere.

When I had the plugs changed (at around 30,000 miles) before the change it was perfectly smooth, afterwards every so often it has a bit of a lump at startup that goes away as the engine warms. Things it could be a) improper plug gap, b) one of the spark modules has gone bonkers, c) connector to plug module had gone bonkers,
plug from ECU has gone bonkers, d) wires between ECU and spark module has gone bonkers.

The only way to track this down is to get the car wired up to an ignition analyzer and then let the car sleep overnight and have all the analysis gear attached, up and running, and observing as the "start" switch is pressed. You may only get one chance per day--make the 1st one a good one.

 

I recently had similar symptoms on my S550 coupe. The symptoms did not clear after warm up however. In my case it turned out that the high pressure fuel pump had a short and that somehow caused a fault in the engine control unit. After both were replaced under warranty all was well again. Good luck getting yours sorted!