You can start with some very needed information.
Version of InDesign and operating system.
How did you fix this? I'm having this same issue on Mac OS X 10.11. When I try to add a page or drag pages in the pages palette my system is locking up, (spinning wheel) in Indesign CC 2017.
For anyone else who is running into this, to get around this I've figured out that rather than dragging a page in the palette which causes the endless loop, I can hit the fly-out on the side of the palette and then add a page or pages where I need them. The system seems to do this method without issue.