I've been having the issue whereas after 20 - 40 seconds I would get DC'd to login, even on character select.

A potential fix could be;
Opening "Properties" on game shortcut - "compatibility" - "Change High DPI Settings" - Tick " Use this scaling...." - Under the dropbox choose "I open this program"

You might have to mess about with this but it solved it for me. I have "Use high DPI scaling" Un-ticked. Never changed it yet my problem was solved.