I am having the same problem since upgrading to Big Sur. I am on MacBook Pro (16-inch, 2019, 64 GB. 2,3 GHz 8-Core Intel Core i9.AMD Radeon Pro 5500M 8 GB / Intel UHD Graphics 630 1536 MB). When I disable the automatic graphic switching it gets a little better but I have to reset the Mac 2/3 times a day . I am using just Zoom/Slack/Safari. What´s going on?