Yesterday I installed my new Zen5 Mainbaord, and installed the new driver package, but I had the issue that I couldnt shutdown my laptop, it always restarsts.
Using shutdown.exe /s, helps so he turned off correctly, then I disabled fastboot, that also helped.
I deciced to reinstall a fresh windos. but know I have exactly the same problem. I attached some screnshots.
I have read elsewhere that the NVME Samsung drivers have had issues in the last few years. They make awesome SSD drives but the drivers, I will pass on! Glad you got it figured out! Congrats!