Oil Pressure at startup is always higher than after warmup. The important parameter would be oil pressure after thorough warmup. If it is low at that time(below .5 Bar) would be worrisome.

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles