Allegedly, on or about 12 December 2018, home user via users sent:
Something keeps trying to do automated updates, but I have not been able to figure out what, or how to shut it off.
When you log into a GUI session, the GUI can fire off things as you log in. In MATE, there's a "mate-session-properties" tool to control these things. Gnome has something similar (slight name change to the command). KDE, likewise. Similar for other desktops.
In my mate-session-properties I see a "dnfdragora-updater" entry was pre-installed. I un-ticked that to stop it looking for updates. Like you, I do updates when I want them to happen.
And I'm subscribed to the "updates" mailing lists, which gives me far more information about updated packages than the GUI tool does. I also get to hear about packages that I haven't installed (that can be a blessing and a curse). The update info is in my mail, where I can read it when I want to, rather than some GUI tool interrupting me with alerts.