Apple has just seeded the second beta of iOS 9.3.3 to developers for testing purposes, two weeks after seeding the first beta of iOS 9.3.3 and three weeks after the public release of iOS 9.3.2, a minor bug fix update.
iOS 9.3.3 is a relatively small update, focused on bug fixes and performance tweaks behind-the-scenes. While this is the second developer beta of the software for the majority of iOS-based devices, it is the first iOS 9.3.3 beta for the 9.7-inch iPad Pro, which saw issues being updated to iOS 9.3.2 recently.
The second iOS 9.3.3 beta can be downloaded from the Apple Developer Center or over-the-air with the proper configuration profile installed.
Are you trying out iOS 9.3.3?