what could make my dodge overheat

I have a 2000 Dodge Intrepid R/T with the 3.5L Magnum engine. It overheated a couple weeks ago while stuck in freeway traffic on a hot day. It did so every day thereafter until I took it to my shop. It turns out the electrical connector at the fan assembly had melted and the fans were not running. Replaced connectors. Everything runs cool again.

ck fan operation as stated

When does it overheat, in traffic, at a stop light, running down the road? How do you know head gasket is "fine", combustion leak test performed?