Yes, it does happen, usually (as was said) water/moisture gets into some of the circuits and shorts them out enough to start them up.
Earlier this year our PowerTech 8.0 KW liquid cooled gen fuel pump would run all the time and the gen would quit after a few minutes. Kept trying to run it and it finally kept running and the pump would quit when turned off just like normal. Never did figure out the cause but it's working fine now.
Oh yes, we need more info like brand/model/fuel type etc. when posting.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Lifetime GS Member, SKP, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '14 CR-V