Is this a problem with one document or all documents or something in between?

You may want to review How to Troubleshoot Problems that Occur When You Start Word
How to troubleshoot problems that occur when you start or use Word - Office | Microsoft Docs

Does it happen if you open Word in Safe mode?
Open Office apps in safe mode on a Windows PC - Microsoft Office

Safe mode is not a way to regularly use Word, but it is a valuable diagnostic step. If your problem goes away when you use Safe mode, we can walk you through other steps that may help eliminate the problem. Please write back.