Stereo intermittent !

[Dsportdan]

Not sure what's causing this problem but basically some days I start the car and the stereo works fine on radio but when I go to change source to either cd/aux/usb or Bluetooth it doesn't do anything it just stays on radio. Then later on in the day or other days it works ok again. It's not the usb I use as taking it out or even formatting it doesn't make a difference, also when it's playing up even my phone won't connect. Any ideas where to start as its not under warranty anymore.
Cheers