My car shakes when it comes to a complete stop. Why

Hello, I suspect the EGR or IAC systems. That is, exhaust gas recirculation and idle air control systems. If the EGR valve stays open when you stop, i.e. sticking, you will have a vacuum leak at idle, and if the IAC valve is clogged, you will not have enough air to run the engine smoothly at idle. You also may have a vacuum leak or clogged PCV valve (positive crankcase ventilation). Shake the PCV valve, you should hear a rattle if it is good. And air should only flow through one direction. Take a spray bottle with water, and spray the engine one spot at a time while listening for the engine tone to change. This will tell you if you have an external vacuum leak. Also, the brake booster may be leaking, and pressing the brakes could be making the leak larger. Press the brakes and see if that makes it run worse at idle.