I went over a big bump the other day and the T quit running(15 touring). It was a short distance from the house so I had no clip leads, multimeter, or tools. No coil buzz though.
It started up and ran fine about 10 minutes later. After I got back to the house I checked for bad connections, corrosion, voltage drop, etc. .... nothing! Everything was top notch.
Which got me to thinking, can the coils themselves bounce up in the coil box to lose contact? I have the correct coil box, correct lid and clipped down as it should be.
With a good box/lid/contacts/coils why wouldn't the car re-start for 10 minutes? Even if they did lose momentary contact which I doubt. I can't see this happening with everything mentioned being correct/good.
Could there be a loose connection somewhere, either the switch, the lead between the magneto and coil box? A bump could move a loose connection just enough to make it quit. And in cold weather setting for 10 minutes could cause something to move just enough to make contact. This is one type of problem that is hard to find. It would be supposed that if the bump caused the coils to bounce, that not all would stop at once and you would have a missfire. Also after the bump they should go back into position unless the spring in the contacts within the box were flat. Then too, what is the chance all would go at once. Leaves me to the conclusion the problem is between the bottom contact in the coil box and the magneto/or battery. If you have a battery and it wouldn;t run on either battery of magneto, it would be more likely to be between the switch and the coil box.
Good luck on finding the source of your problem and fixing it.
Jiggle the switch handle while running at idle. See if that does anything.