I just got a new custom computer with:
INTEL CORE i7-12700K - Core i7 12th Gen Alder Lake 12-Core (8P+4E) 3.6 GHz Intel UHD Graphics 770 Desktop Processor
Mushkin Redline RGB 32GB (2x16GB) DDR4 3600 MHz C16 Desktop Memory-Black
Mushkin Enhanced Pilot-E 1TB Gen3 M.2 NVMe Internal SSD
and a NVIDIA GeForce RTX 3060 graphics card.
BUT all I’m tyna do is the famous Blender Donut tutorial and my computer keeps lagging like crazy at the geometry nodes.
I have no other programs open.
What is going on? Its driving me insane, I got this computer to avoid this problem.
Welcome to BA 
As you are working in Blender, what is your task manager reporting for CPU, GPU, and memory usage? The task manager isn’t super accurate, but a ballpark number will help you pinpoint what’s going on.
In addition to that, what other processes do you have running? I don’t mean open programs- what processes are active in your Task Manager? If the cursed AntiMalwareServiceExecutable (windows defender real-time), for example, is running, your computer is going to lag and slow down like crazy. Turning that off is extremely complicated, but possible, and it will 100% speed up your computer. There may be other processes running slowing you down as well
Other things to consider: what version of windows are you using? What version of Blender are you using? How many tabs do you have open in your browser? What browser are you using?
Oh also, is Blender using the integrated GPU on your i7, or your 3060?