My son's Toyota has an interesting symptom. When I plug in the iPhone to the USB cable, turn on Siri to get turn by turn directions, but stop the podcast or Pandora to achieve silence (my wife doesn't like music, but we still want to hear Siri tell us where to turn). if I nudge the volume knob or the volume buttons on the steering wheel to adjust Siri's volume, whatever source that was last playing will start playing again. Maybe this is what's happening in your Volt? Either you our nudging the volume, or there's something internal that causes it to change.I have an intermittent issue with my 2017 Gen2. I'll be playing a podcast or something from my iPhone, I'll shut off the car and as I am about to get out the podcast will suddenly resume and I have to manually stop it.
I've tried a number of variations (bluetooth instead of plugging in, hitting pause on the screen before turning car off, hitting pause on the iPhone before turning car off, etc.) but they all randomly exhibit this issue.
My suspicion is that I am so slow getting out of the car that it thinks I want to sit for a while and want my radio to keep playing, kind of how it leaves the lights on until you've had a chance to walk away from the car. But does that make sense?
I may also be an outlier in that I usually leave my phone in the car instead of carrying it away every time I stop.
This is with an iPhone5, but I also saw it with the iPhone4.
Anybody else seen this happen?