Start/Stop Music playing when power is supplied via the USB cable

I'd like to use an old(er) Android phone as a Music Player left always connected in my car. I have an ignition controlled USB socket in the car, and would also connect the 3.5mm jack to the Aux In of the car. Is there a way to set a Music Player (e.g. MediaMonkey) to 'continue' playing when power is supplied to the USB charging cable, and then stop when power is disconnected? The reason I'd like to do this is because the Infotainment system in my car (Mazda CX-5) is horribly slow to start up, and music on USB memory stick or played over Bluetooth from my phone takes 2-3 minutes to start up (whereas music connected via the Aux-In starts up almost immediately). I have Android Auto and that's even worse! I've searched this (and other) forums without finding anything that does this simply. Thanks!