freezes are usually caused by RAM. if your OS is not reporting any errors. either RAM isnt 100% compatible or faulty. you might have to manually tweak your RAM since its default settings may not be working with your system. did you enable XMP? have you tried just manually setting RAM clock settings in the BIOS?
if you are inexperienced, you might want to watch the video from the link below to make your RAM work
https://overclock3d.net/news/memory/how_to_manually_set_up_your_ram_speed_timings_and_voltage/1
you can also run memtest86 or just go ahead and use windows memory diagnostic tool. both these are very basic and will NOT tell you your RAM is 100% okay with your system. so do teh 1 stick usage first until it crashes. and do the other.
you need to double check your Event Viewer logs during your times of crashes. it could just be a driver issue or a corrupted windows. you can try going for the fresh install method and reinstalling all your latest drivers from the motherboard support site (starting with your chipset driver). and also your BIOS if necessary.
if it still persists then its sure to be your hardware. its better to do everything you can fix on your RAM or your PSU before ruling out its your motherboard. you can try removing your GPU and see if your system still works okay.