Hi,
I’m running openSUSE Leap 15 on my Lenovo notebook
lately I noticed that update manager posts a notification: “new updates available”. So, I click on view, the package updater window opens, checks for new updates and then tells me “all packages are up to date”. WTF?
So, I open a terminal:
zypper ref
zypper up
and this confirms, no updates available.
So, I assume the package manager feels neglected and is looking for attention from his user.
Cheers
Bernhard
When you feel cheated by this, do as many of us: switch the updater off, or even de-install it. 
It seems that the software updater is configured to automatically update your system.
When you first saw that notice, your system needed updating. But somehow it was then updated behind the scenes.
The update applet is different for different desktops. I normally use KDE, and it is easy enough to tame the update applet. I don’t think it ever automatically updates, though perhaps it can be configured to do that. When I try Gnome, the update applet does rather more, though I’m not sure what.
Which desktop environment are you using?