Car suddenly overheats, then cools down and drives normally

Do you know if the cooling fan works ?
Have you checked the coolant level in the radiator ?

is this happening with the A/C on or off?

At idling speed an engine does build up a lot of heat and the cooling fan will kick in. In slow moving traffic or traffic jams the temperature gauge can touch the red - particularly on hot days. The reason it cools down when you start moving is because of the air flow through the radiator.

Presumably there are no leaks from the cooling system otherwise you would have mentioned it. In normal circumstances the fan will not be running as you are driving at speed, as the air-flow through the radiator is sufficient to cool things. The fan only kicks in to get rid of excess heat - and this usually occurs at idling speed or after you have parked the car.

If the fan is running all the time as you drive, this points to either a fault in the fan switch, or the car is running too hot. presumably in normal driving the fan isn't running and the temperature gauge reads normal?

It is common - in stationary traffic many cars overheat (particularly big engined models) try to stall and 'cut out'. Restarting can be difficult until the engine cools down.

Is your car overheating in normal driving conditions or just at idle speed? Overheating in normal driving conditions can be caused by things like a failing water pump, blocked radiator, collapsed hose, faulty thermostat or, in the worst case scenario, cylinder head problems.

Overheating at idling speed is 'common'. Check your coolant level. If your car isn't using/losing coolant then there probably is no major problem. You can flush out the cooling system and refill with new coolant - and also check your radiator. Are the cooling fins crumbling with age? Or maybe they're partly clogged with insects and debris from the road? A blast with a hosepipe wil sort that out ..

The question is how much does your car overheat in normal driving? If it doesn't .. it appears as though you have nothing to worry about as such. Most cars have 2 speed fans... the 2nd faster stage kicks in at some point dependant on engine temperature. Perfectly normal.

check the condition/tightness of the drive belt/belts , also check the cooling fan is cutting in at the correct engine temperature, hope this helps

have the thermostat checked it could be stuck open or closed it cools down from your fan

I have written a tip on this.
You may have a couple of problems. I would first replace the thermostat, and make sure you have the proper coolant(ant-freeze) level.
Please let me know how it goes and if you need further help I am here.

You are leaking coolant somewhere. Are there any wet spots on the ground when the problem occurs?

Your coolant level could be low,

The cooling fans will not come on until 225 degrees. Normal temp is around 199-215. Sitting still in traffic most will inch up around 220 or so. When you turn ac on it turns the fans on and may cool down engine, Check fan operation.

Many cars have a thermoswitch threaded into the radiator that activates the fans when engine exceedes normal optimum opperating temp. This sensor may have failed , or one of the 2 wires that go to it may have come unpluged or broken