Constantly asking to reboot My android phone (can give more details if helpful) has started to show a dialog after 1-2 minutes after booting:

Reboot to update network setting?

(My translation, network settings refers to mobile telephone network, not WIFI etc.)
There only is an OK button, and the dialog cannot be closed or ignored. And after rebooting, it shows up again after 1-2 minutes.
The problem showed up after crossing the border into another country.
Does anyone have an idea what the problem might be, and how to get this to stop?
I found out that the last system update had been downloaded, but not installed. After installing it, the error disappeared.