2010 e350 saloon auto.try to select d or r and it keeps going back in to park,sometimes it will start to move then stops and goes in to park.done it 3 times in 12 months,shows no faults on diagnostic tool

 

There is a small battery under the dash that provides power to this electronic shifter. Have you ever replaced it or have seen a battery warning pop up?

 

sounds like the car thinks the driver door is open. Do you ever get door ajar warnings for no reason?

 

I don't think that happens on our cars. I tried it the other day an it didn't automatically put it in to park.

 

Do you have keyless go? Happens to me with keyless go when engine running and car is stopped or moving at like 1 mph (haven't tried at a higher speed). Not sure if OP has keyless or not...

 

I do have keyless go. I was stopped, opened the door while my car was running and the main couster turned red and gave me a warning(can't recall what it was) but that was it.

 

You're correct. I tried it to be sure and that's what I got also. Not sure what I was thinking , but I recalled this happening to me. Must have been with the engine off and trying to roll car in neutral in my driveway after turning car off.