its not good. needs to get to full temp. you are creating condensation in the motor doing that, and its not burning off. this is corrosive for internal engine components. if you are going to run, it let it run for about 20 minutes. also the oil never gets fully warmed up in 5 minutes. let the fan at least cycle once. .02
as far as cold starting, i can get my carburated 45 year old 2 strokes to come right to an idle and run just fine in cold weather. then again, they don't rely on rubber diaphragms to lift. If you know how to tune and repair and maintain a carb, not an issue. I was just asking how common an issue it was amongst the c10 owners.