System reboot by itself!

Hello Everybody;

At the last time one of my servers have an automatic reboot by itself and i dont why ??

Here are the output of the 'last' command;

[root@jester ~]# last
root pts/0 xx.xx.xx.xx Sat Dec 8 18:10 - 18:16 (00:05)
reboot system boot 2.6.9-55.0.6.ELs Sat Dec 8 17:31 (2+17:32)
root pts/0 xx.xx.xx.xx Sat Dec 8 16:45 - crash (00:46)
reboot system boot 2.6.9-55.0.6.ELs Sat Dec 8 16:41 (2+18:22)
root pts/0 xx.xx.xx.xx Sat Dec 8 16:12 - crash (00:28)
reboot system boot 2.6.9-55.0.6.ELs Sat Dec 8 16:10 (2+18:53)
reboot system boot 2.6.9-55.0.6.ELs Sat Dec 8 14:53 (2+20:10)
root pts/2 xx.xx.xx.xx Fri Dec 7 12:08 - 12:29 (00:20)
root pts/1 xx.xx.xx.xx Fri Dec 7 12:08 - 12:42 (00:33)
root pts/0 xx.xx.xx.xx Fri Dec 7 12:08 - 12:27 (00:18)
reboot system boot 2.6.9-55.0.6.ELs Fri Dec 7 12:04 (3+22:59)

In google i've read about it and they says this could be when the servers load is too high, but its not a certain diagnostic...

Well any tip or help, will be very helpfully!.

Regards!

 

Any errors in your logs?

 

Has the machine rebooted automatically only once or is it happening often ?