Problem

Had an issue on one of my site collections where clicking on page layout and site template settings would take a long time and eventually result in a time out. Attempting to create any pages from the page layouts would also result in the same timeout issue.

Solution

Reactivate the SharePoint Server Publishing feature under the Manage Site Features on the site collection.

1. Browse to your site collection -> site settings
2. Click Manage Site Features
3. Deactivate the SharePoint Server Publishing feature
4. Reactivate the SharePoint Server Publishing feature

You should now be able to access the page layout and site template settings without the timeout.