Similar thing happened to me driving home in a Big Thunderstorm from Syracuse Nationals. Went through a construction zone and slow traffic caused my car to start to overheat. Then after construction, there was a decline in the road so I put it in neutral to get it cooled down quicker. Then my starter started running while my car was coasting. Had to pull over and get the negative cable off the battery to get it to stop. while waiting for a tow truck, I decided to hook it back up and it started and went back to normal and made it how. The next day the starter was shot. Not sure what caused the initial problem (maybe heat related), but it gave me one last start to get home. Had to have something to do with the wiring or contacts of the starter.