Is it my CPU, motherboard, or another component?

Hello! I'm hoping to maybe get some insight with some issues that I've been having with my PC as of late.

Specs are listed, let me know if more detailed needed: Motherboard: MSI Meg X570 ACE AMD AM4 — CPU: AMD Ryzen 9 3900XT — GPU: MSI Ventus GeForce GTX 1660 Super — PSU: Corsair RM850x 850 Watt — RAM: Corsair Vengeance RGB Pro 32gb (2x16gb) DDR4 3200 — Cooling: MSI Mag CoreLiquid 240R — SSD: 2 Samsung 860 Evo Series 2.5 1 TB — HDD: Seagate Ironwolf 3TB NAS — Case: Phanteks Enthoo 719

So a couple of weeks ago, I noticed that my CPU temps were running higher than they typically would (around 90c) so I did a full run through of my tower by dusting it out. The temps still remained in that area, but I wasn't having any performance issues whatsoever, until a few days later while playing a game the lag was awful, so I restarted my PC to help the issue and got met with a "CPU overheating" message on startup.

After that message, I turned it off and went online to get some new thermal paste, assuming that was the issue. Cleaned off the previous thermal paste and applied the new one a couple days later and there was still no change in temps. It's now around 99c idling when I had it on after changing thermal paste.

Turned it off again and figured it could be an issue with my cooler, so maybe took too far of a leap in buying a new one. Got the NZXT Kraken 280mm.

At this point, I had my dad and brother helping me and we spent hours deep cleaning the tower, ensuring everything was properly plugged into the their places and nothing was potentially loose, in the motherboard or anywhere else.

After installing this new cooler and booting up into the BIOS, the CPU temps were better, around 60c but slowly began to go up and up again. Then got the dreaded "CPU overheating" message again and I haven't turned my PC on since. I do recall the motherboard temp being around 20c in the BIOS when I booted it up.

I'm just a bit lost as to what the issue could be. This build was done in September 2020. Never had any issues since this happening so suddenly. My dad has a build of his own and wants to maybe use my old cooler in his to see if it was actually malfunctioning. Also planning to take the PC in to a shop at some point, but curious about what people here might think.

Again, I included all details I could but please feel free to ask for anything I missed. I'm moving soon, so dropping too much money outside of things related to the move isn't a big priority, so the PC is gonna stay behind until I figure things out.