Since you must take it in, be sure the shop uses ONLY OEM bits for the two idle valve breather lines and the CIS boot. I also recommend OEM for the valve cover to head and valve cover to air cleaner assembly.
If you understand the concept of a nut on a bolt, you can at least remove the air cleaner assembly and take a look around.
M103+W126 cars have an issue where the exhaust downpipes come into contact with the idler arm bushing or the caster rod brace when the motor mounts sag. Changes are you are feeling this on start up. Use only OEM mounts, others are garbage. BTDT.