I normally leave my wipers in the 'Auto' position and forget about them, leaving them to work as required. (Had a Renfault where you always had to turn them off and then back on which was silly)
This morning we had nice coating of ice on the windscreen, almost like frozen rain. I am used to not using the wipers until the screen has de-iced due to the damage that can be done to the wipers and possibily the mechanism. Just as I scraped the windscreen at the bottom, near the wipers, the wipers decided that they were free and also required as the sensor was covered. When they burst into movement it made me jump and didn't do the rubber blades much good as they scrawped across the ice.
Have moved the wiper stalk from the 'auto' position now and will try and remember to do this everytime I park overnight in the colder weather.
Thought this might be of use to someone else.