try to test the oil pressure. make sure its at safe levels. in the mean time, replace the oil pressure sensor. if its gone bad, it will usually do what you described. usually more unpredictable. otherwise, its more like an oil light than a guage. it doesnt give you real time pressure readings. just "Its good" or "Its bad". which is why it seems normal, and then drops to zero pressure. it has a certain pressure threshold, and if it drops to a certain psi, it reads as 0. never seen what too high pressure does though.
2002 GT 5sp. 16x,xxx miles
Steeda Exhaust, C&L plenum, BBK Throttle Body, Steeda Underdrive, Steeda short throw, unknown stage clutch. Rear main leak. Compressor seal leak. Steeda lower control arms. good tires.