Here is my experience. My son's 2000 C230K has about 115m. After sitting for 3-5 days, the car would start with a tremendous death rattle. Engine would briefly sound like it was coming apart. Not just a whine or squeal or minor roughness, this was a scary metal grinding rattle. If the car was driven daily, it was fine. Besides the occasional rough start, car runs normal.

I first suspected the kompressor. Checked out fine. Then I changed the camshaft adjuster magnet. This is the hat shaped thingie at the front of the engine. No change. I then changed the timing chain tensioner. No help there either. Car still sometimes has that scary start when not driven for a few days.

So far these are the parts referred to above. Can anyone sort these out?

hydraulic cam chain tensioner
cam advance unit
cam belt tensioner
cam adjuster solenoid
cam adjuster mechanism
cam chain tensioner

Thanks