Madam Bak

Radio/CD display in my C6/2006 usually shows time (when radio is off), but now, after few minutes driving, the display changes into a white/blue display. see attached pic.
It looks like a kind of display used to setup the radio/CD system?

I'm not able to turn it back to usual display, until engine has been switched off for quite some time. When starting up again, the sequence above repeats itself.

Any advice how to solve this issue is very welcome.