How to check transmission fluid
What does your owners manual say?
Presumably your Mercedes has “lifetime fluid” and no transmission dipstick. Here’s how to proceed: https://mbworld.org/how-tos/a/mercedes-benz-e-class-and-e-class-amg-how-to-check-transmission-fluid-388835 Among other things, you’ll need to buy a dipstick. Sad but true.