What causes the engine of an Audi 80 to overheat?

I recently noticed my Audi 80's engine temperature rising rapidly while driving on the highway. I had to pull over and let it cool down before continuing my journey. What could be causing this issue?

One possible cause could be a malfunctioning thermostat. Make sure to have it checked and replaced if necessary.

Another reason could be a lack of coolant in the system. Check the coolant levels and refill if necessary.