Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
By overheating do you mean you can hear the audible chime coming from the dash and the "HOT" word coming up in the cluster display? If it only happens shortly after cold start up (1st 10mins) it's most likely a sticky thermostat taking too long to open or if it's a longer intermittent overheating, intake minifold gaskets, heater tap or radiator could be the issue. All common well known issues to mechanics. Hopefully nothing major