Same sound I think
I have the same type sound. I have a 1992 300e 2.6 at startup I get what sounds like a rapping from the motor. Increases or decreases with the speed of the engine. Sounds like valve train. I am going through about a quart of oil every 700 miles or so.
Could the rap be associated with a warn valve guide or seal??
PS> I have seen other posts on the site stating for some models it's normal to have a rap at start up.