Could be the motherboard in the back of the
ICC (The central dash unit with the radio, A/C buttons, screen, etc). The solder joints on the board start to seperate/dislodge/corrode /whatever the technical term is
... and things stop working.
I've replaced a few
ICC's over the years (in different cars) when this has started happening... but late last year we decided to have a go at fixing one instead.
I took the
ICC out, and pulled the motherboard out of the big rectangular metal box at the back of it (not the CD player... but the one with the big main plug on it)... then I gave it to my mate James who's good with electronic boards... and he touch soldered all the solder joints on the board... then I re-installed it and put the
ICC bac together.
That was around Sept last year and everything is still working reliably
Before you try this yourself, just note that the car won't start once the
ICC has been removed ( I've got other cars, so didn't matter for me). I've also got a couple of spare
ICC's (kept some previous stuffed ones) so I had back up.
If you choose to fit another
ICC, you'll probably need to get it security coded to the car (though, sometimes you can be lucky it just works). Car will start but the rest won't work until it's coded.
Good luck sorting your issue
D