If you're sitting idle for 10-15 mins, that's going to happen in just about any car, especially if your ambient temperature is high enough. About the only thing you can do is increase the RPM's of the engine a bit to move more refrigerant and make the engine-driven fan blow a bit more air across the condenser. Mass flow of the refrigerant matters a LOT. When you're idling, you have very little mass flow, so the system can't move a huge amount of heat.

Additionally, if your car is black (I bring this up because of your signature photo), you can amplify the effect since the car's skin both absorbs and radiates additional heat into the vehicle and onto you. In a hot climate, dark colors aren't your friend in the summer. I drive a black Honda and a Midnight-blue Mercedes and it gets in the triple digits here in the summer. A/C struggles at stop lights...

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]