Help me, tech support, you're my only hope!

My computer has been shifting window focus on its own for several weeks now. I cannot find anything about this online, & 1 tech friend who looked it over couldn't solve the issue. It's now gotten so bad that gaming has become almost impossible - it can randomly swap out of FFXIV 3-4 times during a single boss fight. It is decidedly worse this past week; sometimes I have to FF because it'll start happening every 10-15 seconds (no joke).

I am horribly tech illiterate (like, I know the 'on' button & very little beyond that). I'm pretty sure I'm running Windows 10. I know my graphics card is NVidia - but can't find where to look up the actual make (they move things around every time they release a new Windows version, grrr - & why do they put it all on my lawn?! ). This happens regardless of what program(s) I have open in the background, & it doesn't even always shift to the same thing anyway - & often doesn't fully shift (though my desperate clicking on the game window to try to get it back could be a factor there).

I'm to the point I'm ready to chuck the thing out the window & buy a new computer, but have no idea if that would even fix anything if it isn't a problem with my system in the first place!

Anyone have any ideas WTH is going on here?