Welcome to forum and happy holidays.
Try doing a search on the site, searching for things like knock, knocking, etc etc.
Also check for oil. When is the last time it was changed. what is the viscosity?
Also what grade fuel are you using?
Have you run any injector cleaner in it?
These are all things that if not done should be checked and or done.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.