How can I determine the cause of random device reboots? After being annoyed with my previous ROM, I thought I'd install ICS on my SGS2 (until CM9 comes out). But, sadly, it now reboots several times a day without any real reason. The device is just lying there on the table doing nothing and every now and then the screen turns on and I can watch it reboot.

So, how would I start to analyse this issue? Obviously I could try to flash different ROMs like a mad man until the issue resolves itself, but I would prefer a more sensible approach.
I had a similar random-rebooting problem, and after one such reboot, I hooked up the phone to my laptop and ran "adb bugreport" on it.  I got what looked like useful information, and attached it to the bug.  So I think at least some log information survives a reboot.

Here's the bug, btw: http://code.google.com/p/android/issues/detail?id=24118