most users forget memory XMP mode is OC 
Have you HAGS enabled, possible try disabling.
In a first step I would check the GPU temp which is easy possible wiht help of taskmanager.
Reboot can in some! cases also caused from driver side, e.g chipset. Checked the mainboard drivers ?
PS.: and “system managed” pagefile setting does not works for some users. It cause not an reboot, instead a CTD, but just for your info.