workaround for this problem
This started happening to my 2017 Volt a month ago, and yeah, it was intermittent at first, but now seems permanent.
If I'm in my garage, I just exit the car with my keys, plug in the recharger, and go inside. After something like 15 to 30 minutes, the car turns off by itself.
Don't know if that will work if the recharger is not plugged in, but I will probably do that experiment at some point.