I have same issue. I bought a new IMAC in December. When the computer goes to sleep or I walk away for a short period of time it takes 30-60- seconds for the internet to kick in. I have Big Sur. It doesn't matter whether I use Safari/Chrome or try to open app and application I cannot access it. I have called tech support every week. We have done every test known, and video taped the problem using quick time, and have done a data capture which was forwarded to apple twice. It has been escalated a number of times, but same issue. If this is a BIG SUR issue can we go back to Catalina until it is resolved! Can someone explain why I have to repeat my issue every time I call tech support. Do they not keep notations of what was done the last time I called. I have wasted hours and hours trying to resolve this. Losing my patience with apple. Love apple but common lets address this......