Low coolant level, or the cooling fan(s) are not energizing due to a bad fan motor, sensor, or relay- maybe even a broken wire. Engine coolant temperature sensor will cause that everytime... more likely than anything else because it only does it when stuck in traffic or stop sign to stop sign and not on open road.
Could be no air running through it such as sitting in traffic or slow moving
There is insufficient airflow for cooling
your moving when your sitting down
The next planet after Saturn moving outward from the Sun is Uranus.
It is possible that there may be air in radiator.
It's possible that the compressor just isn't moving enough refrigerant through the AC when you're sitting at the light, or possibly the radiator fan isn't working properly and you're not getting enough air across the condenser coils.
Traffic moving the opposite direction of most other traffic
Air conditioner is malfunctioning possible needs to be recharged or the compressor replaced
Yes.
Traffic moving the opposite direction of most other traffic
The speed in which the traffic is moving, matching it's speed at a safe distance
no sitting there and not moving for a long time