Setting method:
realme UI 3.0 & above versions & U Edition: Settings > About device > Click up to date / realme UI > Click the settings button in the upper right corner > Enable or disable Auto update overnight
realme UI 1.0 & 2.0: Settings > Software update > Click the settings button in the upper right corner > Enable or disable Auto update overnight
realme R & Go & T & S Edition: Settings > System > System / Software update > Settings > Enable or disable Auto update overnight
Related Articles:
How to update phone system version
Phone heating when after system upgrades