Premiere Laggy and eating up 100% CPU

I'm having this annoying problem after updating my Premiere Pro CC to the 2021 version.

Every time I open a project, my computer slows way down for about 10 minutes, and in my task manager, I see that Premiere is eating 100% of my CPU. I've never had this problem before the update, even with lots of chrome tabs open, AE, Photoshop, and folders. But now, even if I close everything, I still have the same problem for about 5-10 minutes. Mouse dragging, everything laggy, and suddenly the percentage goes down again, and I can work properly.

This only happens when I open Premiere.

My pc specs are:

Asus TUF X-570 Plus

Ryzen 9 3900x 12 Cores - 24 Thread

HyperX 64GB RAM

GTX 1070 ti 8GB

I appreciate your time and help.