Good PC, absolute garbage performance.

My PC is from September 2021. Lately, I have been having trouble in every single game I play (being the only known exception Valorant) because the performance is horrible. Not only I can't get 60 fps, I can't even get 40 stable, and fps drops are as frequent as pressing space to jump. The only solution I have right now is restart the PC, but that only works once. If I stop playing and then want to play again, then I have to restart again. The bad performance affects even desktop tasks such as navigate through files and searching through the browser. When I write, letters take up to 3 or 5 seconds to appear. Here are the specs:

Case: DarkFlash DLX21 Mesh Cristal Templado USB-C/3.0 Negro

Storage 1: WD Purple 3.5" 2TB SATA3

Cooler: MSI MAG CORELIQUID C360 Kit de Refrigeración Líquida

Motherboard: MSI MAG B560M MORTAR WIFI

CPU: Intel Core i7-11700K 3.6 GHz

Supply Power (no idea how to say this in English): Thermaltake Smart RGB 700W 80 Plus

One additional fan to get air out: Tempest Fan 120mm ARGB PWM Ventilador Suplementario Negro

GPU: Gigabyte GeForce RTX 3060 GAMING OC 12GB GDDR6 Rev 2.0

RAM: Corsair Vengeance RGB Pro Optimizado AMD DDR4 3200 16GB 2x8GB CL16

Storage 2: Kingston A400 SSD 240GB

There's no specific order in the list because I got the names from the page I bought them, and I didn't buy in a specific order either. If you need any more information, please say so.

I also have to say that, if it's not obvious, this has never happened before, and that the PC performance has always been more that I asked for. The temperature is always below 60º, most of the time below 50º, and I have never overclocked it.

Edit: I only play on native resolution, which is 1920 x 1080 for me. I'll save money and try to get a new SSD. Thanks for the answers.

Edit 2: The monitor is plugged into the GPU, not into the motherboard. I double checked just in case.

Edit 3: I've read comments about virus and crypto miners. If I reinstall Windows again (deleting everything in the process), will any virus or crypto miners be deleted as well?

Edit 4: I will delete everything and see if that helps. I think it'd probably take at least an hour to see if that's the problem. This time, unlike the other 3 times (if I didn't count wrong), I will use the SSD only for the OS. I had a few programs installed there because of two things: the friend that helped me to get the parts and build the PC said it's good to have the game launchers in the SSD (Steam, Epic Games, Ubisoft launcher...) because they'll load faster; and also because sometimes I couldn't find the option to download this or that in the HDD. I will upload my findings.

Edit 5: I have played Hogwarts Legacy with the same configuration that I had when I didn't have the issue I'm talking about (which made the game go at 60 FPS with minor drops, being those drop literally 1 to 3 fps for a split second and then back to normal for a whole other 10 minutes). The game is running at 20 FPS, with drops that go as far as to 11 FPS. However, the PC doesn't sound any different, and the 20 FPS are actually somewhat stable. I don't know how to use HWiNFO64, so here's what Dragon Center shows me while in game. Photo because I can't put it directly here. When I played the game without the issue, at 60 FPS constantly (or 75 because sometimes I switched to 75), the temps weren't as low. They were closer to 60 degrees, although it never reached said temp. In fact, it looks to me like the PC isn't even trying to perform good, given the fact that the temps don't change between in game and off the game. I will play one Valorant match (long one) and see the temps.