is the “Service Engine” light on?? if yes, did you scan to check which code is set?
also is the 350Z turbo or NA?
when does the engine overheat? while running or parked?
does it happen while the A/C is on?
do you have any after market parts on for added performance????
stuff you might need to do.. is service the radiator by cleaning it and cleaning the passages.. make sure the radiator has a clean air passage, which means there is nothing that could clog the passage between the radiator and the A/C radiator or the transmission cooler if Auto.
you could also check if the catalytic converter isnt bad, but you should get a code if thats the case