It's very rare for a CentOS box to crash, but recently one of our boxes was crashing at random times.
In order to work out what was happening, I used the "crash" software that comes pre-installed nowadays.
To start with, you need to install the kernel-debuginfo package (yum install kernel-debuginfo).
If it's not available, go into /etc/yum.repos.d/CentOS-Debuginfo.repo (or stream equivalent) and set enabled=1.
You then need to go to your crash directory (typically /var/crash), and load up the crash report with the following command:
crash /usr/lib/debug/usr/lib/modules/$(uname -r)/vmlinux vmcore
It will then tell you what happened and with what piece of software.
In our case we saw:
PANIC: "BUG: unable to handle kernel paging request at ffffd6963eab17a8" PID: 76524 COMMAND: "chrome"
Indicating an error in Google Chrome (which we'd just updated).
If no crashes are stored, make sure kdump is installed and running, and check settings @ /etc/kdump.conf