It could be the motherboard but without some specific error code or some "by elimination" troubleshooting I cannot say for sure.
However, with the problem now occurring 1 of 4 times that is certainly an improvement. However if the RAM are not fully matched (purchased as a kit) for dual channel use then memory could be the root issue.
This motherboard?
https://media.s-bol.com/Bnx1GRw6DXXo/original.pdf
[Do verify that I found the correct/applicable User Guide.]
Referencing the User Guide, two things must be done:
1) Verify via the User Guide and a visit to the manufacturer's website that all installed components are supported. Be sure to check the QVL (Qualified Vendor's List) on the website. Especially RAM.
2) Once all components are confirmed as being supported: again refer to the User Guide to ensure that the corresponding configuration settings are correct for the build.
For both 1. and 2. above, details matter so pay close attention to fine print, caveats, etc.. Remember there may have been some changes so visiting the manufacturer's website is important. And remember to check the manufacturer's FAQs and Forums.
Temporarily, stop any overclocking, turn off power savers, Simplify as much as possible with the objective being to obtain a stable situation = 0 in 4 times of occurring. Then you can start making changes again but making only one change at a time plus allowing time between changes.
And although Reliability History and Event Viewer are not showing any errors etc., keep checking. At least Reliability History because it is easier to work with and understand. And if some event of any sort appears then the timeline may help discover what happened to cause that. So keep track of what you do and change.