An AC that starts and stops with loud clicks may have a failing relay, contactor, or thermostat

https://samedayhvachelp121.urbanvellum.com/posts/24-7-hvac-repair-the-most-common-after-hours-ac-problems

An AC that starts and stops with loud clicks may have a failing relay, contactor, or thermostat. Avoid repeated resets and schedule a professional diagnosis.