This exists solely to game fuel efficiency tests, because the tests were/are designed with long periods of idling.

They basically added a feature that uses more fuel in 99% of real world scenarios, to beat fuel efficiency tests in a controlled environment, then greenwashed it as a fuel efficiency "feature". Isn't capitalism fun?

They knew the structure of the tests beforehand, and regulators haven't changed the tests, because we live in corporate dictatorships masquerading as "democracy".

Kick them so hard they're kids fall sleep when they stop moving too long.

The dongle getting place

It’s an OBDEleven. It only works for VW, Audi group cars though.

An example looks something like this

(It shows an one adapter in the first image but it shows an actual harness further down)

I didn't see one for Mercedes on that site, but it sounds like it mentions the existence of them here under method 3

Installation usually involves:

• Accessing the wiring behind your start/stop button

• Installing the module inline with the existing harness

• Securing the module in a hidden location

That page also suggests that you may be able to disable it with a programming tool on some models. Depending on what you have I'd give that a try first