Random yet consistent Computer lag

Hi, My computer is fantastic as far as all the tech and gear inside of it as I even just bought a new fan. for over 3 years this computer has been doing wonderful no problems whatsoever. Just recently I started getting lag spikes if I was on one thing (like a browser or a game) and clicked on something else. it's really frustrating and I have no idea what caused this. this is a video of what happens ( https://www.youtube.com/watch?v=Zb-YAqhA4Zo&feature=youtu.be ) Don't know what caused it or why it happens. (Task Manager : https://gyazo.com/5967102d10c1ac300879dd5ada9c0a99 )

Sometimes, maybe for an hour at a time the computer will work fine and there would be no problems, but most of the time it's a problem. But nothing's out of the ordinary as far as I know? Anyone have any ideas? windows 10 btw thanks.