OK.

Diagnostic 1: Start Word in Safe mode.
Do you have the same problem? If "yes" I don't have a solution, yet.
If no...

Diagnostic 2: Close Word and rename the normal.dotm template.
Normal Template in Microsoft Word - How to Find or Open the Normal Template
Same problem? If no, the problem is in your normal.dotm template. Otherwise, if yes, close Word and rename your old normal.dotm file back.

If no problem in Safe mode and renaming normal.dotm doesn't cure it, you probably have a very poorly written Add-In. Add-Ins in Microsoft Word