I have a 2009 Ducato based motorhome each time I start the engine the wipers start up even though they are turned off, it happens every time I start the engine

Many years ago I saw this on my fathers car, it turned out to be a bad earth...... we cleaned & greased the earth strap & connections and the problem went away.

Definitely a bad earth somewhere. Check your engine to chassis earth cable and clean terminals if rusty or otherwise bad.