Thanks for reaching out. We are sorry for the trouble with Lightroom Classic. If you can clarify a few things for me, we can get to the bottom of this.
Could you please share the version of Lightroom & the operating system you are working on? Do you see any errors, or does it get stuck? Does this happen when editing images from a specific set or collection?
Where is the catalog stored? Is it on an internal drive or an external drive?
Are you using multiple monitors? Does this behavior appear after a series of steps or in any screen mode like fullscreen?