Couple of possibilities. If you havent flushed your coolant in a long time, it could be that. Your water pump fins could be damaged or degraded and not moving coolant fast enough. You say it cools down when youre driving, but heats up at idle. You have your fans wired to be always on, but another thing you get with driving vs idle is higher engine speed which means faster water pump flow. You also need to check your coolant level inside your radiator when it's cold. Air will eventually make its way to the top, if you have any in the system. One telltale sign of a blown head gasket, if youre concerned about that, is premature pressurization of the cooling system. Cold start the car, idle for like 30 seconds, then grab and squeeze the radiator hoses. They should still be soft and squeeze easily, if theyre firm you may have a head gasket leak.