With CM10.1 I've experienced another kind of (soft) reboot,not really random: sometimes when waking up the device only the button leds would light up and a few seconds later the startup animation would start (a soft-reboot?).
Today I've disabled the lockscreen and had no more reboots while waking up the device. It's a bit early to say anything, but it seems likely the lockscreen has something to do with it (or my specific lockscreen config, which includes a couple of extra apps and a custom icon stored in the sdcard).
EDIT: Two days later, the reboots when waking up are still gone. I'm guessing they're definitely lockscreen related...
I had this problem... I found that "automatic brightness" was the cause of it. I never had one random reboot after disabling that option and setting brightness manually