Firstly, welcome to the forum.
It doesn't only happen when there's a full moon does it?
This must be a nightmare for you, I had similar, but not as outrageous, problems with the E Class merc I recently got rid of. It regularly let me down because of flat batteries, I used to carry around one of those booster packs to save calling out Merc's recovery service!
I'm convinced that a lot of problems are caused by modern cars having too much (and in some cases unecessary) techie gear.
Sorry that I can't offer any advice but I hope you get it sorted out.