Diagnosing spontaneous reboots?

[tripwirecc]

The last couple of days, almost everytime I boot my machine up cold, running startx (I don't use dtlogin) fires up the X server, remains at the patterned default background and then it crashes and reboots. The second attempt then works.

Other than that, the 8800GT of mine seems to work fine.

Is there a way to fetch crash logs or whatever to diagnose where the problem is?

Thanks.

[zander]

One possibility would be to set up a serial console and run with the kernel debugger enabled; instead of rebooting, the system should then trap to the debugger, allowing you to get a stack strace, etc..