Engine shuts down and will not restart when elec

You need to make sure you have good voltage everywhere. That means voltage testing. Make sure battery has a full charge and connections all clean and tight. Check that the fuse circuits have good voltage, voltage testing. Some fuses are hot all the time, some go hot when you turn on the key. Any applicable trouble codes? If security system is losing voltage, it may go into theft-lock, in that case, the starter may not even crank.