See also:

Mercedes-Benz M-Class Owners Manual
...

Before changing a fuse
  Park the vehicle and apply the parking brake.   Switch off all electrical consumers.   Remove the SmartKey from the ignition lock. The fuses are located in various fuse boxes: ...

Even more agile: sports suspension and Dynamic Handling package as an option
In addition to the standard-specification AGILITY CONTROL suspension, the C‑Class offers two other options for adjusting the suspension's characteristics in line with drivers' personal prefe ...