I have an issue and it sounds familiar but not totally. Typically it happens about once a month, but occasionally its during a long trip (towards the end) - and this leads me to think overheating. My radio will just cut off but the screen will still be lit up (I have the Nav, DSP). I can power off and power on and the radio will work again for a 1-3min. A lot of the time the screen stays on but will "freeze" and sometimes it will switch to a static/white screen.
At first I thought I'd just buy a new radio, but honestly it works perfectly 95% of a month, but there is always a day or so where this pops up. This past week I made a 300 mile ride and about 10 miles from home on the way back it started. So I started to think its this issue or maybe an mixture of two different problems.
its a 2000 528 with Nav,DSP