I've been trying to diagnose this issue for over a week now with no luck. Every 4 seconds my mouse and keyboard stutter for a fraction of a second and on random rare occasions my screen flickers black with a few verticle lines. The screen flicker happens so fast, I can't see how many lines or their color. Video (VLC, MPC, YouTube) also seems to have a slight hiccup at the same moment as the mouse and keyboard but audio (Pandora, iHeart, WinAmp) does not.
So far, I've tried checking for viruses, trying different mice and keyboards, made sure all drivers were up to date, tried rolling back drivers, tried power management settings, CPU utilization settings, etc etc etc.
This issue does happen in safe mode as well as bios.
As of now, I am leaning towards it being an issue with the PSU but can't be certain. The voltages seem to be staying in appropriate range, according to my HW Monitor. The only certain thing I know is that the hiccup happens like clockwork, every 4 seconds and that the CPU drops to 0 mhz when that happens. Could this be a motherboard, cpu, psu issue or something completely different? Greatly appreciate any help!
Specs:
Windows 10 x64
Gigabyte H270 Gaming 3
i7-7700
32GB Ram
GTX 960
800w PSU
So far, I've tried checking for viruses, trying different mice and keyboards, made sure all drivers were up to date, tried rolling back drivers, tried power management settings, CPU utilization settings, etc etc etc.
This issue does happen in safe mode as well as bios.
As of now, I am leaning towards it being an issue with the PSU but can't be certain. The voltages seem to be staying in appropriate range, according to my HW Monitor. The only certain thing I know is that the hiccup happens like clockwork, every 4 seconds and that the CPU drops to 0 mhz when that happens. Could this be a motherboard, cpu, psu issue or something completely different? Greatly appreciate any help!

Specs:
Windows 10 x64
Gigabyte H270 Gaming 3
i7-7700
32GB Ram
GTX 960
800w PSU