I have a 2017 250d GLE , the issue is the air con starts off really cold then goes warm then goes back to cold when driving but not every time it seems to be intermittent. Sometimes when you start the car the air con stays warm until i turn the engine off and start it again , then it goes cold, also the air con smells when its first started. The car has had its cabin filters changed and a full re-gas and shows no leaks or problems on the diagnoses.
Thanks in advance for any help

It sounds like your GLE is going into "EPA Sleep." You should have a button next to the push-to-start (or elsewhere depending on year/model) with a circle with a slash through it. Push it every time after you start your car and the problem should resolve.

I have a similar problem with my ML164 2006.
Just been told that the problem is an overheating coil in the aircon compressor, which causes it to cut in and out. Apparently quite a common problem. Hope this helps.

If something was like you're describing the Auto Start-stop button.

The feature shuts off the engine to save fuel when you are stopped, and can be disabled with that button.

Yes an engine not running. Wouldn't drive the air conditioner compressor, but I don't think that's the problem that's being described.

He might get more feedback if he posted in the w166 forum.

I’ve just discovered that intermittent Aircon operation can be related to a fault with the overhead control unit near the mirror. Can also cause the automatic wipers to run all the time. Maybe this helps. Apparently there is a little fan in there which may be stuck. Someone recommended blasting compressed air in there to free up the small fan.

Interesting situation.
What's your car? Your profile says "2006 ML320cdi Sport." Correct?