Overheating issue

My car's recently started overheating occasionally. It only does it in the hot sun while I'm stopped in traffic. The temp will start to rise, and my low coolant light will come on. I've checked, and the radiator is topped off with fluid. The first time it got almost in the red, and I turned the heater on and the temp dropped down quick. It's been a week without overheating, and now it did it again today in traffic, luckily I got out of it and got back up to speed, and it dropped down to normal.

I tried to duplicate the problem once I got home... parked the car, left it running, as soon as the temp would get slightly above 210, the fan would kick on and it would go down... I couldn't get it to overheat again.

What could be causing these random overheatings? Is the fan for some reason sometimes not kicking on when it should?

sounds like the fan relay or the fan motor not kicking occasionally. or even the coolant temperature sensor could be going bad.

change the fan relays out first. that doesnt cost much and takes maybe 2 seconds to change out.

are you overheating with the a/c on? because the fans kick on with the compressor on automatically regardless of ANY coolant sensor reading.

investigate the fans.