#!/bin/bash
 
# You could run it from cron e.g /etc/cron.d/updatesystem with the line below it it
 
# 0  4 * * 7     root    /usr/local/bin/cronscripts/updatesystem >/dev/null 2>&1
 
# Remember to uncomment the cron entry line, and then copy this script to
# /usr/local/bin/cronscripts/updatesystem
# Remember to restart cron i.e systemctl restart cron.service
 
#
# Getting package list
#
apt update
#
# Updateting system
#
/usr/bin/unattended-upgrade -v
#
# Wait for things to settle then reboot
#
sleep 5m
reboot

Note: # If you need to configure unattended updates there is a script [ Here ] you can use.