I would be concerned about the condition of the A/C compressor. If it is causing too much drag on the belt, you could see the engine struggle to return to idle, but that should only be momentary. Does it completely turn off? Does it return to idle after a few seconds?
RepairPal Certified shops can diagnose and repair your 1996 Mercedes-Benz C220. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.