The pinwheel that you see at top-right of the screen is a network activity indicator. This indicator can be expected to appear whenever a process/App is accessing your WiFi network and the internet.
Sometimes a background network process can “get stuck” and cause the this indication to appear unexpectedly - or to persist for extended periods. The simple solution is to restart your iPad; whilst the indication may initially appear again for some hours while background processes “catch-up”, normal performance should return quite quickly.
To restart your iPad:
- 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.