Server reboots - OS or centminmod?

Yesterday I had a scare with my newly purchased dedicated server. I logged in SSH and saw that the server was rebooted a few minutes earlier. Soon after that, the server became non-responsive. I had the host restart the server and run a hardware test.
This is the response

Is there any log or anything I can check up on to figure out the issue why the server reboot on its own and become non responsive and to eliminate issue like this in the future?

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Thank you

 

It's reliablesite
Is there any log showing history of the server reboot and which actions caused it?