KBCobra

I have a question about my head unit for those familiar with it or similar hu's. When I start the car, within 1-10 minutes, my speakers mute and I get a double beep everytime. It never fails. I have the GPS and Bluetooth connected so I figured it would be a connectivity signal. Its not either of them because the GPS gets signal instantly as soon as the unit is turned on and the bluetooth on my phone is turned off so theres no signal there between the two. I have searched without luck. There was a person on an F150 forum with the same problem but his question was not answered. Any ideas?