This happens to me when editing games with hundreds of thousands of baseparts. I think it’s just a side effect of that. Seems to happen more when at the edges of the map if the camera is pointing at the rest of the map. It’s usually less severe when pointing the camera straight down to limit the parts in view.
You can also take parts of the map out to another studio instance, make your edits, then bring it back in and line it up using primary parts and the command bar.
I certainly don’t have a potato PC so ignore @Billy_Dodo’s non-constructive reply. It’s to do with having too many parts with infinite render distance and no automatic LOD.