This is normal operation for MB vehicles.
Other makes calibrate their gauges to register nominally at all times...you may be used to those characteristics.
If you haven't already noticed, your coolant temp gauge will register all over the place...especially during the summer.
So don't fret unless your oil pressure drops to almost zero at any time, or your coolant temps get above 120 C.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car