ML320 rattle engine noise

[Marc]

I have a 98 ML320 with 107000 miles on it.
It runs and shifts fine but the last week or so I'm hearing a rattling type noise when you shift into gear. Upon further inspection, when the car is in park or neutral, you will hear the noise just every once in a while at idle. If you shift into a drive gear forward or reverse, you will hear the noise all of the time at idle. If you step on the accelerator the noise goes away. The noise seems to be coming from the upper front area of the engine. Only thing I can thing of is timing chain. I also have an 83 500sl when it needed a timing chain it just rattled at startup until it had oil pressure. This does it all the time at idle.

I would appreciate any thoughts or direction to a related post.

Thanks