This has happened three times now. Libre Office Writer apparently starts to auto-save, and then perpetually shows the hour glass. I’m forced to restart and lose 1/2 hour of work every time. I’ve had no problems like this until recently. I’m on Winsows 7, 64bit, the latest Writer program as of 11/20/2018. [Update: It happened a 4th time now.]
You can configure Writer to save autorecovery data every x minutes. If that works and your computer crashes, you can recover the latest autosave. Autosave data will be deleted if Libre closes normally. So you still have to save your work regularly.
On my slow Windows 10 pc Libre runs slowly, some dialog boxes take a while to load. Your computer is probably older, and may therefore be slower still. in that case you should probably disable any features that you don’t really need, like showing sample text in font lists, but also autosave. If you save your work every ten minutes or so, there’s not much need for autosave, anyway. It’s also possible that you need to refresh your user profile - see https://wiki.documentfoundation.org/UserProfile