Do not disturb on iPhone will not turn off

If Do Not Disturb activates itself, then an automation may have been set up.

Go to: Settings > Focus > Do Not Disturb > find "Turn On Automatically"

If there is a period of time, tap in and select: Delete Automation.

You can read more about Focus here:

Use Focus on your iPhone or iPad - Apple Support

Not the Control Center in Settings, but the Control Center on the Home Screen. You can actually access the Control Center anywhere on your iPhone and iPad.

Pull down from the top right corner of the screen and look for the Focus Button, The one with the moon symbol. This can be done on both your iPhone and iPad.

See also this animation:

Does Do No Disturb on your iPad also start automatically? Have you tried a simple restart and have you disabled Share Across Devices, both on your iPhone and iPad?

Deactivate here:

Settings > Focus > turn off Share Across Devices.

If Share Across Devices is activated and you activate DND on your iPhone, then the function will also activate on your iPad and vice versa.

Okay - I can see that. Try to follow Lawrence Finch's advice, quite simply. Pull down your Control Center from the top right corner. Find the Focus button, tap. If you see Do Not Disturb highlighted, tap to disable.

Also try restarting both your iPhone and iPad. Turn them both off and wait a minute and turn them back on.

Open the Control Center (Access Control Center on your iPhone - Apple Support) and you can turn DND on or off with the Focus button:

Swipe down from the battery icon on an iPad to open Control Center and tap on the Focus button, the same as on an iPhone. It should look like this:

Try unlock your iPad and place your finger on the Wi-Fi and Battery icons in the upper right corner and drag down. Then you should bring up the same Control Center as on your iPhone.

You aren’t looking at the Control Center on the iPad.