I watched some YouTube video of Biden’s 2012 debate with Paul Ryan. Some of the same verbal tics are present, but they are much more subdued. I think there is something else going on here.
My best guess is that it is mild short-term memory loss. I have experienced this myself, and I’m younger than Biden. The good news is that, if I’m right, it doesn’t impact his ability to process information, which is really the bottom line for him as a candidate and potential president.