I do not like to see generators exposed to those conditions ever put into service without some sort of heater that energizes on cold conditions. When a generator starts, it quickly goes to full speed in order to provide the correct frequency AC power. Normally, engines do not like this abuse! Your dealer should be able to guide you re available options.
The starter pinion drive gear is sticking.... its the smaller gear on the shaft that moves up and down to engage the flywheel gear and start the motor. Carefully put a LITTLE hi temp grease on the shift splines (curved ones) and see how much that helps. The gear is not staying "retracted"..if this doesn't help.. the spring that pushes the gear back down may not be strong enough...(you could always fix both)
With the brand name of a generator, this does not matter in most cases, but it may happen that the circuit breaker is defective or is only ejected, nevertheless, always use a multimeter for operating reliability, if that does not help the second thing Is a large capacitor intern where the plug blocks are located mostly at the rear of the generator.
The capacitor may be deformed or even short-circuited in rare cases.
fault finding repair tips for brushless capacitor compensated generator
Could be the load you have on it is to much for when it does it it self .when you do it do you turn power off then start it and then putt the power back on .then it would run easy every time .could be your back up battery for it is to small .is it on a transfer switch like it should be when it starts it self .