You need to open your Normal template, accept changes, and turn off Track Changes in that template. Erase any text. Then save. That should handle it.
Normal Template in Microsoft Word - How to Open

An alternative, if you do not have other customizations saved in the Normal template, would be to find and rename that template with Word closed. Then reopen Word.

If that does not solve the problem, chances are you have a really strange Add-In.