Some projects in Premiere Pro become very slow, especially playback with in the timeline lagging, after a few hours of use and then the only way to get it back to normal performance is to exit the programme and reboot the computer. Rebooting Premiere or my graphics driver doesn't help. It is especially bad when working with a project that uses a lot of images.
After restarting the PC, things are back to normal for a while. What can be causing this? It has happened to me using various versions of Premiere.
If that doesn't work, try resetting the Workspaces: Reset a workspace Reset the current workspace to return to its original, saved layout of panels. 1. Do one of the following: • Click the Workspace menu icon and select Reset to Saved Layout. • Choose Window > Workspace > Reset to Saved Layout. from here: https://helpx.adobe.com/premiere-pro/using/workspaces.html
If that doesn't work, try Preferences > Audio Hardware and set Input to None.
If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site. If NVIDIA, do a clean install of the latest Studio Driver (NOT the Game Driver)
If that doesn't work, try creating a new project and import the old one into it.