Engine turned off while running and now will not crank

Was sitting at stop light, car running smooth, went to take off and engine turned off. No sputter, just turned off like if key had been turned off. After that, I get nothing when I turn the key to start. Checked all under hood fuses, all good. Under dash ignition relay clicks when turned to on and starter relay clicks when turned to start. All lights work, battery shows 12 voltson tester. Tried replacing ignition switch, no change. When key is turned to start, engine does not crank at all.

If it was starter, it would not have turned itself off while running. What else should I check?

Also, when testing ignition switch at plug, one wire always hot. Turn key to ACC and another wire is hot. Turn key to "on" and a third wire is hot. Turn key to "start" and no difference from "on", just same three wires hot.

Ended up being the #18 fuse, under dash. Amazing to me a 15A fuse would shut down the car when driving. Not sure what caused it to blow.