cause of reboot

[Emre Çamalan]

Hi,
my server reboots every night and same o'clock last 10 days. But this machine's uptime was 96days.

Suddenly reboot this machine and now this continue every night again and again.

I didn't find any reason and I didn't change anything else.

I looked "last" command, 
reboot ~ ~   AM 03.15  ~


I checked "dmesg -a" , it has only generic things no other things.

I checked "/var/log/messages"

I wrote script and checked swapinfo , cpu and memory but all of them was normal before reboot.

I checked crontab and scripts.

I checked "crashinfo"  but no dump from kernel.

I didn't find any useful info from this commands.

I checked "praudit /var/audir/20130930..CrashRecovery"  
and I didn't understand very well from this file but I think this means my machine crash and reboot isn't it??

And How can I understand what is the reason of rebooting my FreeBSD8.3 server.

Please help I need to find cause of reboot..