In most modern vehicles, you do not need to enter a code to activate the stereo every time you start the car. The car's audio system is usually integrated with the vehicle's infotainment system, and it will automatically turn on and connect to your phone or other audio device when you start the car.
However, if your vehicle does require you to enter a code every time you start the car, it is usually a temporary security measure that can be disabled. You can typically find the instructions for disabling this feature in your vehicle's owner's manual.
