Turn on Windows Task Manager and watch for activity on the disk drive where your video files are located. If it jumps to 100%, then something, probably your anti-virus program, is scanning the drive/object. This happens to me sometimes, but it only seem to happen on one drive. Once scanned, 30-60 seconds, I can work again. Still to be resolved somehow.
Are you logging in to the computer with a Microsoft account and using OneDrive to backup your files?
If so then this may be the cause of the 'pausing'. You need to stop OneDrive synchronising the folders that VDL is using for your projects, you can see which folder this is in the Program settings, Folder tab, Project entry.