Ethernet keeps disconnecting
I had similar problems years ago for many months.
Intermittent disconnects temporarily resolved by rebooting
disconnecting CAT5 cables and reconnecting
Windows Network Properties software configuration changes
all would fix the problem temporarily then random
disconnections.
CALL your ISP provider: Comcast, Verizon or whatever.
Request the central office test your line,
and ask for a technician visit if needed.
My problem was poor cable connections outside
on the telephone pole and other connection points
on exterior and interior: up to three or four connections
were serviced.
(Apparently the cumulative effect of 3 or 4 connections
physically degrading by oxidization, corrosion etc.)
Only after Comcast Technician visit was the connection
drop outs resolved.