recently I was having online game issues so ran a speed test.
discovered downloads were fine but uploads were 1mbps.
that is ONE megabits per second.. my network box is on an UPS and has not rebooted since maybe last year. turned off router, waited a few mins, plugged back in and download/upload speeds normal. try rebooting all network hardware.

another time was having network issues and discovered a wifi driver update did not go well.

would not hurt to check your windows files. open a command prompt with admin permission and run these commands
sfc /scannow
dism /Online /Cleanup-Image /ScanHealth

(sfc scans and repairs Windows system files
dism fixes corrupt files in the Windows system image, use it when SFC can't repair files)

might not be of any help but there are some logs in folders

Documents\Elder Scrolls Online\live\logs
...\steam\steamapps\common\zenimax online\launcher
...\steam\steamapps\common\zenimax online\logs

check windows event viewer and also windows reliability history.
might be a game crash event or system related problems.

with no error msgs, could be many other things. the game worked until recently so something changed. last week my windows desktop got 2 windows KB updates, an nvidia driver update, and an intel bluetooth and wireless update all on the same day. did your machine get an update or did you install a new program/monitor/service?