'95 Geo temperature gauge

I’d like to thank everyone who commented on my last question about the type of fluid to use in the manual transaxle of my ancient but mostly faithful Geo Metro… Took it to a real mechanic as suggested (instead of Jiffy Lube) and he performed the task at a reasonable price…



This morning my temperature gauge started going crazy… it wasn’t overheating but the needle would go from normal to cold and back several times…



Would this indicate the need for a new gauge, something more complicated like a thermostat or are my car and I just getting old? Thanks in Maryland

The prime suspect woul be the coolant temperature sensor (or its wiring/connection).