Columbus unit periodically not working

Hi

We have a Skoda Octavia 2011 fitted with a columbus unit for radio and navigation. In periods, this does not start with the car. This is after a longer stop, typically overnight. Turing the engine on and off does nothing. Then after leaving it overnight, it might suddenly decide to work just fine again. It has not turned off while driving and not turned on while driving either. It is completly unresponsive and does not show even the time, and does not play any sound.

If this could be fixed easily, we would be so greatful, and if not, poining us in the right direction would be very helpful. 

Hope someone can help