[Steve Kirkham]

I would check for carburetor icing. This has happened in exactly those conditions.

Air outside is close to freezing. When the gasoline vaporizes, the air cools tremendously. Moisture in the air and gas freezes on your venturies, in effect 'choking' the carb, same way a choke valve does.

Then you sit, the carb heat soaks, the ice melts, and all is good.

Check: next time it dies, quickly pull the air cleaner and look for ice in the air intakes.