5.3 spontaneously rebooting

[casey at phantombsd.org]

Due to FBSD's stability, I have never had to diagnose a kernel stability
problem before!! Lately, my server has been rebooting itself for an
unknown reason. There isn't anything informative in the logs. I can't find
any core dumps (find / -type f -iname '*core*'). Can someone point me in
the right direction towards diagnosing this?

TIA,
Casey