The onboard should have a low value (high current) resistor in line if left constantly on. Full throttle + power to the plug can burn out the plug. I would take a resistance reading on a glow plug, and use a resistor of that value. (essentially providing .6 volts to the plug)

That combined with a bit of aiflow reduction at the cylinder head would cure the problem if its too cold.

Another possiblity.. carb icing. if there is the TINYEST amount of water in the fuel.. you will have ice form in the carb and the engine will die. The ice will melt before you get to the airplane.

BTW... flying in cold weather I used to use 25% nitro to prime the engine but still filled the tank with 10%. Just needed a little extra 'kick" to get em started. But I never flew in below Zero temps. (I hate being cold.)

I have flown when it was raining, snowing, sleeting.... Had to land once due to ice forming on the wings.