x2 on the oil pressure sender. Had this same issue on my SDL. Was reading 3 and ~2 at idle, then suddenly wouldn't go above 2 anymore and would "flick" the needle at idle.

Replacing the sender solved the problem with little effort.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]