I have the near-exact motherboard you have Z390M AC, I have Z390 AC. I had crashing issues as well.
My solution was to remove:
OneDrive.
(other solutions say re-install)
Also: you can't run ram that slower than the motherboard's recommended lowest speed.
RAM for Z390M ( 2666/ 2400/ 2133 MHz ) it will give you random rebooting and crashing issues as well
If you are going to remove any programs this program is better than MS's uninstaller:
Geek Uninstaller - Download
geekuninstaller.com
it removed the program files, the folder, and the registry entries whereas MS uninstaller always leaves the folders and or registry entries.
my setup:
i7-9700k, RTX 2060 KO 6GB, 32GB of ram
running on two NVME running raid 0.
Windows 10 - v1903