My 69 GTX has a strange thing, Last year when I started the car for the first time of the season, it ran fine, for about 5 mn, then stopped running, like someone turned if off, never did it again last year, this year same thing, ran about 5 mn and it just shut off, but it starts right back up and is fine, any ideas for the cause other then a ghost ? Fuel or Electrical is my guess and thinking its the latter, car is mostly stock except for Electronic Ignition. Thanks

Coil connections?

Bad connection, corrosion
It warms up and shuts off, it gets hot and expands to make that connection go open, next time the current jumps the bad connections and welds some metal into that connection and last until it sits log enough the next winter for the corrosion to eat it up again

Decades ago, a buddy had a GTX that would randomly shut off while driving: turned out to be the dist wire to the points had chafed and would ground to the housing.
There are a lot of possible scenarios - but sounds electrical in nature.

Ecu ground
Distributor pickup or wiring, as was mentioned
Bulkhead connection

had one years ago that was a fresh restoration. the car would die when one closed the R door The owner had done the majority of the work and quite a nice job.
He was a retired Lieutenant Colonel from the Air force, a little on the short side, southern accent and a bit excitable so it could be a bit humorous to watch him jumping around the shop🤣🤣🤫

The problem was traced to the female pin that supply's 12v to the control module. When the connector was molded around the pins, that pin was recessed to far and barely contacting the male pin. Closing the right door would break the circuit long enough to kill the motor.
Wired in a new connector harness and end of issue.
I love issues like this that are random

A ballast resistor can do this when it is getting ready to fail, long shot but a cheap check and throw the spare in the glovebox.
Verify the coil wire is not broken internally had one of those drive me nuts for a bit. Found it using an ohmmeter and flexing the wire (bast-rd) LOL
Next you might try a 12V test bulb hooked up to the coil and temporarily run inside the car to a Visible spot. When the car dies if the bulb stays lit you've eliminated power to the coil. move on to the next potential candidate.
keep us posted,

I had a similar problem with my 340 Dart a couple years ago. When the car died while I was driving it, I pulled over to the side of the road and started checking under the hood.. I knew it was electrical and not fuel because everything cut out including the dome light. I just started wiggling wires under the hood (while watching the dome light) until it came back on. It turned out to be a bad connection where the fusible link wire plugged into the bulkhead.