So I've had a Droid since day one of the D1 release and have flashed MANY, MANY ROMs on quite a few different devices.
I've had the Bionic since it's release day and have had pretty good luck with it.
However, I flashed CM9 to it (stopped at build 7/20/2012) and can't get past that build for some reason or another, but that's not the real underlying issue here.
My phone will occasionally reboot itself out of nowhere (just like most other Bionic owners on here) - but I know what's causing my reboots - the radios.
When my phone loses 4G and the bars go white (with no 4G or 3G attached), then all I have to do to get it to reboot on it's own is go to Settings > WiFi and toggle WiFi on and off, OR toggle Airplane Mode on and off. Either one (especially the Airplane Mode toggle) causes the reboot instantly.
That's one part of it - the other part of the problem is that after this happens, it won't boot back into CM9 for anything, getting stuck on the CM9 loading screen until the battery dies (I've tried with a couple different batteries, all charged and ready to go)
If I go into Bionic Bootstrap Recovery and restore to 7/20, everything works but I clearly lose everything I've done since then.
If I go into the recovery and wipe cache and/or dalvik, the phone will boot up but gets stuck on "Starting Applications" and won't go past it.
At some point, I'm going to need to update to a newer CM9, but right now, I just need my phone to work...