You will likely need to seek assistance directly from Apple Support. The Contact Support link is at top-right of this page.
There is an issue affecting some owners of iPad Pro 10.5”, subsequent to updating to iPadOS, whereby the iPad will reboot every few minutes. At present, there doesn’t appear to be a reliable self-help fix or workaround for this issue. Here is link to one of the current discussions relating to this topic:
https://discussions.apple.com/thread/251262928
If not already tried, attempting a full Factory Restore might be worthwhile:
Restore your iPhone, iPad or iPod to factory settings – Apple Support