Im getting problems with my stereo and sat nav on my range rover sport 05

This is what happens when i switch on the stereo it comes on for a couple of seconds then switches off itself the nav screen does the same, nav screen totally switches off where as ther cd player still illuminates but each time i switch it back on cd player just switches back off

I got a message saying system failure system shutting down from the stereo screen

Any ideas what it could be caused by.. Dont want to take it to land rover until i kow the problem

Tony range rover vogue 2011
bentley continental ss 2011
mercedes s class 2010