iPad frozen

Follow all the steps provided here:--> If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

If the issue persists, contact Apple Support directly, using this link:--> Official Apple Support

Regards

Giulio

If iPad isn’t responding, do one of the following:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

Note: If iPad still doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won’t turn on or is frozen.

Contrary to other advice in this thread, you would be ill advised to deliberately fully discharge your Li-ion battery, as doing so can be risky. Unless the battery is new, the battery may not recover - and may render the iPad inoperable.

Let the battery die completely, then do a hard reset.