Your pressure gage is what is referred to as an "idiot gage", meaning it doesn't show what the pressure is at all, but shows only that you have enough oil pressure. Its a pressure switch more than a gage. It will either be in the "normal" position (minimum pressure pressure present) or pegged low (no or low pressure).
The flicking you describe means the gage is getting a rapidly changing impulse from the sensor. This could be a couple of things: a) your oil pressure is hovering around the set point for the gage, or b) you have a bad sensor or gage.
If its "a)", you could be low on oil, have a bad oil pump, a clogged oil pickup tube or clogged return ports to the pan. Remedy here is to pull the oil pan and inspect for goo and strange objects in the pan (there shouldn't be anything in the pan except oil and some sludge). If you have molasses, you'll need to flush the oil system. Check the forum for methods to do that. If all looks clean, then you'll have to verify the operation of your oil pump. Again, check the forum for methods to check your oil pressure.
If you have good pressure (verified), then all thats left is "b)", the sensor or the gage. Of these two, its most likely the sensor. They can get a buildup of goo that blocks the sensor from seeing the pressure. Clean it or replace it.
