Sorry to hear that Lightroom is not responding. We're here to help.
Could you please share the version of Lightroom (Help > About Lightroom) and the version of Windows on your computer? When do you get the error message? Since when are you noticing this? Did you try resetting the preferences?
Try optimizing the directory: File -> Optimize Catalog.
Increase the cache size. Besides, ensure enough free space on the disk where the cache file is located.
Find out where the cache is located and change its size in the Edit > Preferences menu (Lightroom > Preferences on Mac) on the File Handling tab.
Change the value to 5 or 10GB. You may also take advantage of the Purge Cache feature.