I have a 2002 Prius that developed an interesting habit last winter. Whenever the overnight temperature gets down around freezing upon starting the car the next morning I get a Master Warning and the car turns itself off. Of course the manual says to immediately contact Toyota Service but instead I just restart the car and it runs and drives fine but the Master Warning will not turn off until the ambient temperature goes up above freezing. The colder it is the more insistent the car is about the Master Warning because if it is very cold I sometimes have to restart two or even three times.
I would call and ask Tom and Ray on the air but they seem like really nice guys and I don't want to embarrass them.