2013 W221 no sound from the radio
somebody tell me something what's first to check?

Common problem is the amp but I think you really need xentry diagnostic scan

First, check if the sound is gone for all sources like radio, CD, and Bluetooth. If it's completely silent, the most common cause is a failed amplifier in the trunk. Check for water damage on the amp or a blown fuse. A faulty MOST fiber optic loop can also kill all audio.

Alexie is right, sound is transferred via MOST fiber optic cables, sometimes that can be a problem, I believe there's a bypass cable available on Amazon for testing this

two posts in two days - where no one bothered to look for the same issues posted within 24hrs of each other

https://mbworld.org/forums/s-class-w...ml#post9233753