Since we are talking about the oil pressure gauge, it follows that the oil pressure sending unit would be involved. But oil level could indeed be a cause for concern. Back to the basics......have you checked the oil level, with the dipstick, as per the owner's manual (engine not running)? How long since the last oil/filter change?

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Hanno
'79 6.9 Sold (after 27 years)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon