You very well may have a hardware issue, but one thing you can do for testing and to eliminate other possibilities is to remove all the extra packages you have installed. I see pfBlockerNG and bandwidthd at a minimum.
One of those may be causing the reboot. Removing both and then testing to see if the reboots recur is a good first step. If you don't have reboots with both packages removed, then add them back one at the time and test for a while between each add.
If you get reboots with the packages removed (that is, with a plain-vanilla install), then you likely have a hardware issue and Netgate will have to work with you on a warranty fix.