iOS and iPadOS updates seem to be coming out often these days, and setting your iPhone or iPad up to automatically accept these updates is easy as one, two, three!
On either device go to Settings -> General -> Software Updates. Select "Automatic Updates." Here you will see two options. "Download iOS Updates" will download any new updates to your device while on Wi-Fi. "Install iOS Updates" will run those updates overnight when you are charging and on Wi-Fi. Turn them both on to take advantage of automatic updates.