Once in the 70s I was in the factory where I worked and a backhoe that was there the day before digging a hole for a machine base started on it's own. I saw the headlights flash then it fired up. The starter relay shorted out.
Once in my driveway the 1970 Dodge Dart I had tried to start on it's own. It was backing up out of the driveway on the starter motor when I ran outside and pulled the battery cable. The starter relay which was mounted below the battery tray and corroded and shorted out.
New Port Richey,Fl