If you've followed this guide, you will have configured automatic updates. Those get executed every saturday at 18:00 and will cause a reboot of your server afterwards. This is especially problematic if you've configured Pi-hole as your local DNS server for your home network since any DNS request will not work for as long as the server reboots and the Pi-hole isn't reachable. Also, if you've installed Pi-hole it will try to update itself every saturday at 19:30 which causes the same effect if an update is available.
To fix this, you can change the time when the updates get executed. Here is how to do this (instructions)
