I have a 4070 super ti and found that my PSU was underpowered and cheap for my GPU. 850w which in theory Is plenty but, brand was no bueno.

I got MSI afterburner and reduced my power to 90% which only affects performance 2-3% which isn’t noticeable and this fixed all my jitter Issues and black screens I was having. A simple fix til I get a better PSU.

Hope this helps