It’s not about the RAM. It’s about the VRAM on the GPU. I don’t know what kind of corrections you’ve made and how much VRAM you have but according to the Geforce page it should have at least 4 gigs. Unlike Premiere, Resolve uses GPU for pretty much everything when you start adding nodes and effects and whether it can fit in the VRAM depends on what kind of stuff you’re doing. For example if you have a lot of temporal effects that read frames backwards and forwards (like noise reduction) it will need to read more frames into memory thus requiring more VRAM to make that work.
Here’s a quote from the Davinci config guide:
“For processing UHD or 4K-DCI images we recommend 8GB or more of GPU memory. For some operations 4GB will be sufficient. 2GM is not recommended.”
You wrote about noise reduction before so as a workaround you might want to try exporting whatever you have with the noise reduction off. Then bring it back in and make another pass with only the noise reduction.