I've been driving my 03 I35 for almost a year now runs great just reached 134K recently.

Lately I'm bothered by times I start up my car I sometimes get the oil pressure light sensor flickering and Rpm that swings around 1 to .5 RPM originally I was worried that my car might have been burning/consuming too much oil but I checked my oil next day it was still pretty good for another 1 to 2K miles and car still runs like a champ. Should I switch to higher viscosity oil to combat this ? I've searched threads and can't find a clear answer.