no oil pressure?

[GS608]

So not sure if this is an electrical gremlin or mechanical but recently my oil pressure while idling would drop down to 0 and the warning light would come on then once i start driving the pressure rises with revs, after leaving the car overnight start it up the next morning the problem had disappeared, everything would run as normal, a few days later while sitting at the lights it happens again, i parked it and started it a few hours later but it didn't go away til the engine had cooled. About a week later (today) it happened again, this is after I dropped the oil and changed filter on Sunday.

Any suggestions on where to start?