Mine does something similar. Mine will randomly reboot while I am driving. Sometimes it will go three days without doing it...sometimes three or four times in a 10 minute drive.
I took it back to Cartoys and they sent it off for repair. After three months, they sent it back and told me there was nothing wrong with it (with a charge to my credit card, no less).
I JUST wrote to Pioneer customer service and was told that it was a factory repair. They want $185 to repair it. No.