On the basis of your description, your iPad battery is exhibiting characteristic symptoms of a failing battery - that cannot retain charge, or output sufficient current to meet the demands of the iPad.
Charge and monitor the iPad battery - Apple Support
You would be best advised to seek assistance directly from Apple Support - and request a remote battery diagnostic. If you battery is detected as being defective, they will provide appropriate advice.
The Contact Support link is at top-right of this page. Alternatively, you can initiate a support case using the Apple Support App:
https://apps.apple.com/gb/app/apple-support/id1130498044
Alternatively - and arguably a better solution - is to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to “hands-on” test and assess your iPad. You will be in the best possible place to explore your available options:
Genius Bar Reservation and Apple Support Options - Apple