Chasing a cooling system issue

Twice within the last one to two months the temperature gauge has suggested that engine was about to overheat. At least one of the two times the car would not start until after it had cooled off a bit. Both times the radiator coolant level was checked the next day and the radiator was full. The overflow tank also had some anti-freeze in it.

What could be causing this issue?

I do want to check to see if I have a record of the last time the water pump was replaced. I also believe I have replaced at least one of the sensors in the past. Just cannot recall if it was the one attached to the lower part of the radiator or the one that screws into the engine block near where the upper radiator hose connects to the block.

P.S. I have purchased a new thermostat and the sensor that I believes screws into the engine block but I have not installed either one as of yet.

P.S. It does seem like this vehicle has run a bit on the "hot" side for the last few years. Perhaps at the 1/2 to a little above that on the temp gauge.

Thank you in advance for your help.