20 12 Peugeot 308 owner, the engine of my car shakes indirectly after the air conditioner is turned on, and it does not shake when the air conditioner is not turned on. What is the reason?

According to your description, firstly, it is possible that excessive carbon deposition in the throttle causes intermittent jitter of the air conditioner. Because turning on the air conditioner will increase the load of the engine, at this time, the engine computer will issue instructions to increase the throttle opening and maintain the stability of the engine at idle speed. If the throttle has too much carbon deposit, it will lead to unstable idle speed. Second, it is possible that the rubber parts inside the engine bracket are not good. I suggest you check the specific fault point.