Need some advice.

I've been consistently upgrading my old desktop for a long time now; knowing full well that someday it would just not be uppgradable anymore and it wouuld hit it's upper limit.

I'm hoping it's not doing it now, right when computer memory is getting ridiculous. And I don't have the money for a new one.

A couple of days back, My mouse (any mouse) would move in fits and starts. It takes a split second to start moving, and when it does, it's already on the other side of the screen.

This SEEMS to be related to oncee every second, my CPU is "Spiking"; jumping from 40 to 50% to 0-5% ever second like clockwork. I don't know if one is causing the other, just that they correlate to each other. Typing is similar effected; it'll hiccup every second or so.

System Monitor shows nothing unsual. The majority of the resource usage is from Wayland (I'm on Manjaro), with nothing else taking up resources.

Any advvice on what kind of reports I can run to get a sense of what'ss happening, hardware wise?

I've rolled back the most recent update to no effect. I booted up a USB stick version, and had the same problem. So I'm sure it's a hardware issue. I tried various mice and keyboarrds, various dongles, etc... I suspect a power supply issue, but I don't want to spend the money on a new 750 watt PSU without confirming it. And the only other PSU I have in my house right now isn't powerful enough to boot all the hardware I've got installed.

Help please. This desktop is where most oof my work is accomplished (video editing, graphic dessign and 3D modelling) which is completely impossibel with a jerky mouse.