Your problem is slightly different from mine; my Safari behaves okay when first up from sleep, but the longer it's up the slower and worse it gets. I'm using Opera right now and some pages might take a while to load, but the problems are very mild, nothing compared to Safari. I wonder why an Apple tech doesn't give us some different advice on how to fix this, or how they're going to fix it. We've already tried all the suggestions, as if it's something we were doing wrong. Maybe they don't want us to use Safari. It's only my spare browser now, I only open it if something isn't supported in Opera, but other than that I've ditched Safari and spend much less time now sitting, waiting, quitting, reloading and giving up. All these comments in here but no real answers from Apple ⚠😟