This is a fun one. I am slowly leaning towards my GPU might be dying but I would like some expert insight.
 
Every now and then my computer will start micro-stuttering. It stutters almost every 300-500ms exact. Mouse movements, key strokes, windows dragging, all that stuff freezes for a brief moment then jumps to where it should be. Audio never lags out. It occurs most frequently when I launch NZXT Cam or when playing PSO2. When it occurs in PSO2 it almost always begins right after a load screen. I have never had this occur in any other game or software. When it occurs, rebooting does not solve the issue. I just have to wait it out then it disappears on its own. Someone told me maybe something is triggering windows memory diagnostic and its running in the background, but I have disabled those tasks and can't find the service anywhere when this happens. 
 
https://www.youtube.com/watch?v=6PVPVGcE-Rc This is a video I took with the game still running in the background. However, this is exactly the stuttering that continues even with the game closed and after reboot. 
 
I have reinstalled windows. Tried Windows 1909 and 2004. Tried multiple nvidia drivers. The problem never happens if I use my onboard video. I have troubleshot a lot over the past few days and what I have discovered is below. 
 
My specs are:

• Windows 10 Pro x64
• Aorus Master z390
• i7 9900k @5.0GHz
• 4x8GB Gskill Trident @ 3600MHz
• EVGA 980ti
• NZXT Cam and EVGA Precision X1 for monitoring/cooling software

When the stuttering occurs there are 3 threads that get pinned higher than dxgmms2.sys when inspecting System -> Threads with process explorer. ntoskrnl.exe!KeRaiseIrqlToDpcLevel. The issue is they never resolve once the stuttering begins. 
 
I did an xperf with no game running and attached (xperf.png) a lovely little 20s blurb of spikes. Each spike is utilizing 100% of a core. However, it happens so fast task manager never picks it up. Task manager only says ~5% of CPU is being used. If you zoom in on a spike you get to see (zoomed-in-spike.png) that the spikes consist of 2 stacks, nvlddmkm.sys and ntoskrnl.exe. One is the nvidia driver and the other is windows kernel. The driver is firing off 35x more than the kernel based on the count, so I am leaning more towards driver issue. That is why I tried different drivers and whatnot. 
 
Using latencymon (latencymon2.png) there are a lot of DPC counts for the nvidia driver and an equal number for the kernel and wdf01000.sys. No idea if this means anything. I know enough to be dangerous but not enough to make decisions for myself.
 
So something is causing the kernel and the driver to fight each other I guess. And since this build is less than a month old, minus the GPU, I am leaning to the GPU is dying. Sadly, I don't have a spare to test with, nor do I want to buy a new one since the 3xxx series is coming out later this year. Buying now I would be outside of the step up window :(. Any insight would be insanely helpful! I have posted this similar issue to the Nvidia boards with 0 traction. Just someone telling me my system is fine.

5ghz all core on the 9900k? If yes, set it back to default clocks for testing. Overclocks can cause all sorts of issues, so putting all hardware back to default clocks is recommended. Set your ram speed to 2666 MHz as well. Have you also tried the video card in another pci-e slot?

I have tried using stock settings with xmp off and it still occurred. I have not tried a different PCIe slot and will set that up now. 

Sajin
5ghz all core on the 9900k? If yes, set it back to default clocks for testing. Overclocks can cause all sorts of issues, so putting all hardware back to default clocks is recommended. Set your ram speed to 2666 MHz as well. Have you also tried the video card in another pci-e slot?

The moment my computer booted and hit the desktop, the stuttering occurred. None of my monitors or controllers are set to load at boot.

Do you have another pc you can test the video card in to see if the issue will follow the card to another pc?

Sadly no. My old machine bricked the the day I built this machine; what are the odds!

Well then you could always take the card to a local pc shop to see if they can reproduce the issue.

So at this point its basically either GPU or possibly (slim chance) mobo? No other things could be causing the interactions with driver & kernel above?

Someone just informed me it could be the EVGA Nu nahimic driver causing issues and linked me to this post. https://www.reddit.com/r/MSILaptops/comments/7uucrb/everything_nahimic_2_possible_fix/ Old, and not EVGA Nu dirctly related, but does talk about the nahimic itself can be a PITA.  

vgerik1234
So at this point its basically either GPU or possibly (slim chance) mobo? No other things could be causing the interactions with driver & kernel above?

Yep. Wouldn't think so, but could be wrong about that. If you're getting the problem on a fresh install of windows with just the nvidia driver installed then it's clearly a hardware issue somewhere.