If you do not have the current standard chain tensioner installed, have it done immediately. Don't let an independent check the p/n; verify it with a dealer. There are a lot of the superceded ones out there in inventory with parts houses.
Mine failed at idle basically "lunching" one piston, a bunch of valves, etc. Tab: $4K.
The cold temp rattling sound indicates the old style tensioner.
1986 190E 2.3-16 (Decomm rear self-leveling suspension; Euro-code headlamps) sold
2004 Audi S4 6-spd - sold
1969 (2) and 1980 Porsche 911T, S, and SC - alas gone
1987 300SDL - Graf Spee; Euro-code headlamps; 16-inch 8-hole wheels - sold
1994 E420+(E500 suspension/E-code headlamps/PAD chip) sold
1968 250SE 4-speed (NICE car) - long gone
1962 220S 4-speed/column mount - long gone