why does my completly new PC lags and games crashes?

spec:

Operating system: Microsoft Windows 11 Pro, Version 10.0.26100

CPU: AMD Ryzen 9 7950X3D 16-Core Processor

RAM: 32.0 GB

GPU processor: NVIDIA GeForce RTX 4090

3 monitors, max 1080P on all 3

im wondering why my pc lags alot, all drivers for windows are updated (as far as I know) like there isn't any windows updates cus I updated all, all grafik card drivers are updated, and as far as I know the CPU drivers are fully updated to latest cus I looked at couple of tutorials and done it like 2 and a half week back, still my PC lags, and games crashes, like as an example, today when I started my PC, it was really slow, I opened a game that doesn't require a lot of performance at all (VRchat) and I opened it in desktop mode, basically doesn't require any performance at all, when I did it, the game was slow and laggy, like I couldn't even open disk manager, and finally when it did, it took a long time before I could use it, and it was crashing and stopping al the time, I did restart my PC and it helped, but now when I was playing vr, my vr crashed, I mean this cant mean that my PC cant handle the vr, what could be the issue?