Two problems related to engine shut off without warning have been reported for the 2012 Chevrolet Volt. The most recently reported issues are listed below.
The car shut off completely while I was driving 65 mph on the freeway and had to be towed into the dealer for repair. It was determined by the dealer that an underhood fuse shorted out and burned into the vehicle battery charging system causing the car to shut down while driving. A major safety hazard as this could have caused an fire.
Was driving Volt at low speed in traffic. Attempted to switch modes (normal to sport). This is accomplished by pressing a button on the dashboard twice in quick succession. The button is located right next to the start/stop button. I accidentally pressed the start/stop button twice in quick succession, which shuts the car off. The car shut off and I was unable to restart it until I came to a full stop, shifted the car to park, and pressed the brake. The resulted in a small traffic backup behind me. However, this the design and placement of these buttons is very poor. I believe the start/stop button has been designed to shutoff the car relatively easily in light of the recent and public "sudden acceleration" problems by other manufacturers. However, accidentally switching off the car is also an undesirable consequence. Had this event happened at higher speeds (on the highway) it could be quite dangerous.