This happened to me once and the culprit was found to be the starter motor. Everytime the car was hot, the pinion kept getting jammed. Since you have a manual tranny, when this happens next time, put the car on 3rd or 4th gear and move the car back and forth. If it works fine after that, then the most likely problem is there. Costs around 1000 bucks for the repair.
You have a carb engine, so it could also be a vapour lock. This can be solved by heat shielding the fuel lines.
As for battery, if the cold start is ok then the battery is generally ok
As for head gasket - you will have dozens of problems if the head gasket is blown. things like misfires, smoke etc.
Sensor issue is also unlikely. You probably have a very basic temperature sensor in your car
Just giving u a few ideas.