Well , you got a couple thins going on.

1. coolant smell in the vehicle. Most likely caused by a leaking heater core.

2. AC blowing warm at stops, most likely due coolant loss and overheating. As the engine begins to overheat the ECM (computer) shuts off the AC compressor to remove any excessive loads on the engine.

As you begin to drive what little coolant that is left in the engine begins to corculate, the engine cools down and the AC returns.

First thing... Fix the coolant leak before you roast the head gaskets.