I have a 2006 GS 300 without navi.
I had this issue before but I don't know how I fixed it :P . The problem started when I was waiting on my girl but she was taking to long so I took a nap, the screen was bugging me so I selected Display button, then selected "screen off" on the LCD screen, this turned off the screen but music was still playing.
When I start the car the screen shows the Lexus splash screen then goes off but my music will start to play automatically. I press any of the 4 buttons (Display\Info\Audio\Climate) the screen will come back on, I press any of this buttons again it will come off. The way it was before it would always stay on no matter what I press.
I also tried to disable to function that auto transition to certain screens but that had no affect. It bugs me as I want the screen to stay on and not go black when I'm driving. If i adjust the volume the top will show on the display the volume increasing but the full screen is still black. Its hard for me to explain, but I'm hoping someone knows exactly what I'm talking about and can help.
Thanks in advance,