How to find out what causes random reboot via last_kmsg file?

Hello everyone,

Since I flashed CM13 on my S4 i9500, I have random reboots everyday.
I'm trying to find out the reason for this, and according to google results, file named "last_kmsg" can help me with this.
The file location is: system/proc.

How can I find out the reason with this file?
Can someone help me with this?

Here is the file:
https://dl2.pushbulletusercontent.co.../last_kmsg.txt

And here is the download:
http://www98.zippyshare.com/v/lsrBcO7Q/file.html