I don't think it's a short. As you said maybe the battery is dying so the voltage on crank is dropping low enough to cause the reset. Or a bad ground somewhere. A bad ground would cause voltage to flow back through the system searching for a ground somewhere/anywhere. You've probably been behind a car at night with two tailights on, then you get to a stop and the car in front has just one brake light, the other side has no lights at all. Bad ground on the dark side. The brake filament voltage is "grounding" itself through the tail light filament. 12V on both sides of the tail filament = zero current flow = neither filament lighting.