Question CPU Usage at 90-100% when launching Games

Feb 25, 2021
Hey everyone, new here at Tom's Hardware and I'm hoping you lot may be able to help with an issue I've never had up until recently. I am by no means an expert, but I did frankenstein my PC together myself. If I'm in the wrong forum arena, please know. Kinda new to the whole forum thing in general.

Recently, I've had a big issue running into sever PC lag when I launch a game. I can get away with games like Phasmophobia, Terraria, Minecraft, etc. Relatively low resource costing games. However, when I boot up Modern Warfare, Apex, or another more medium to high demanding game I run into sever PC lag. This lag isn't just applicable to the game itself. Its extremely slow when I tab out, try to perform another task, my mic gets muted in whatever chat I'm on, etc. I've never had this issue before today. I run two monitors and have always been able to have multiple tabs and even games running at the same time with no issue. I don't use my Pc for anything other than school work and gaming so it's been a real disappointment to say the least. I suspect it may have something to do with my CPU but I'm not sure.

I run an i5-6600k with a NVIDIA 1660ti GPU. I have 32Gb of ran and the important software is installed on a dedicated SDD. if you need any other info I'll gladly answer any questions. Thanks for your input in advance! I'd really love to get my PC rolling again!