[CMI - 2000/1/12] NSX engines typically don't overheat. One thing to check, especially if the cooling system has been worked on recently, is air in the system. The NSX has a very specific way to fill the system in an attempt to avoid air pockets. Our cars can run at normal temperatures with some air in the system but it will show as overheating when pushing the car hard...such as on a track. I'll also heard it can take a couple of attempts to bleed the system as described in the shop manual to alleviate the problem.
[BSD - 2000/1/12] The solution could be any number of things. First, check the coolant level in your vehicle. When cold, open the engine compartment, and check the coolant fill tank. There should be some coolant in there. There are marks on the outside to show how full it should be. Never open the coolant fill tank when the engine is warm or hot. If that is fine, and you haven't had any recent changes to the cooling system, then you should check:
Radiator cooling vanes. The radiator is in the center part of the nose fo the car. Make sure no plastic bags or other debris is blocking flow.
Electric radiator fan. To check this, start engine, wait for it to warm up, then see if radiator fan cycles on an off.
Thermostat. If both of those seem ok, maybe your thermostat is stuck closed. Get engine warm while parked, and see if temp stays the same. Also, check hoses going from engine to chasis tubes to see if flow pulses through there when thermostat opens.
Lastly, could your waterpump not work well? I haven't heard of a water pump not working other than if it starts to leak.