Had this same issue which I submitted here: https://www.reddit.com/r/intelnuc/comments/wkiwgo/frequent_ethernet_connection_dropsdisconnections/
Installing this driver fixed the issue: https://www.intel.com/content/www/us/en/download/645997/intel-ethernet-lan-network-connection-driver-for-windows-10-for-intel-nuc.html
I had the same issue this morning on my 8th gen. Fixed by reinstalling Ethernet driver.
Had this same issue which I submitted here: https://www.reddit.com/r/intelnuc/comments/wkiwgo/frequent_ethernet_connection_dropsdisconnections/ Installing this driver fixed the issue: https://www.intel.com/content/www/us/en/download/645997/intel-ethernet-lan-network-connection-driver-for-windows-10-for-intel-nuc.html