Windscreen wiper starts in dry weather

Hello everybody, for some time now it always happens that the windscreen wiper starts “OFF” at the switch position, although it is bone dry outside. I also have the impression that it occurs more often than not. Especially this happens with slow driving and narrow curves and/or uneven road. And “no”, I don’t accidentally get to the wiper switch. The wiper switch works intentionally as desired. Do you know this perhaps – best also the Gru nd and the remedy ? Many thanks for your ideas and hints.