I have exactly the same problem, even worse, my Safari just randomly restarts after closing the message of using too much memory. I have Sensi running indicating that Safaris is ranked 5th in RAM usage and using less than 100MB. I have a brand new iMac 27 with 16GB Video Ram and 128GB Ram, so that isn't the problem. Safari 14 is a complete disaster. Nothing is faster than chrome and FireFox. (I refuse to use anything from Google)