I have a 2007 caravan with the factory radio installed. The radio has power as I can see the display and switch channels with the radio buttons and the buttons on the steering wheel. After starting up, I get sound for a couple seconds then nothing. If I turn the radio off and on, same result. I have replaced the fuse with same results. Any ideas?

 

Try pull battery cable for few minute, reset the radio.
but this sounds like you got a bad radio. Radio have internal thermo circuit breaker if there is internal failure.
Maybe you should consider an aftermarket replacement unit, pull one from a junk yard, or Ebay.