Rodney Stovall

I have a 2007 Lexus 460L and the radio goes off while I'm driving. I stop and turn off the car, and it comes back on. It happens about twice a month. I took it to the Lexus dealership and they said it was fine, but it's not, still having the same problem. I got a new head unit from lexus dealership 2 years ago. Can someone help me? Rodney