Comment # 1 on bug 1095674 from Frank Kruger

(In reply to Hot Music Fan from comment #0)
> Hello!
> 
> On openSUSE Leap 15/KDE Plasma 5.12 LTS Network Manager connects to Wi-Fi
> very slow on system start/restart/logout and login. While it tries to
> connect t othe defined network the update checker already performs its
> update check and gives an error notification that there is no internet
> connection.
> I found the reason - because by default Network Manager stores the
> name/password for the current user only in an encrypted way and I assume it
> needs more time for decrypting. Workaround is saving the password in
> unencrypted way (for all users) but for me this is a drawback and it should
> be fixed.

See also https://bugzilla.suse.com/show_bug.cgi?id=1073610