As described, while your iPad is running - it will periodically appear to “freeze” prior to automatically rebooting the iPad. This issue is distinct from a boot loop - as a boot loop is a condition by which the device never successfully boots into a fully running Operating System before restarting and the process repeats. As such, a boot loop can be reasonably dismissed as a potential cause.
Your symptoms suggest that you have an installed App that is periodically crashing, causing the OS to detect an unrecoverable condition that requires a reboot. Does this periodic reboot occur when you have no Apps running? You may need to close all open Apps using the Task Switcher.
Close an app on your iPhone or iPod touch - Apple Support
If the iPad remains stable with no running Apps, you will need to systematically identify the App that is causing the problem. Once identified, delete the App from the iPad - and then restart the iPad before re-installing the offended App from the App Store. Once reinstated, retest.
Should you be unable to identify the faulting-App, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad:
Genius Bar Reservation and Apple Support Options - Apple