A family of Microsoft word processing software products for creating web, email, and print documents.
It is usual to have a blank document open when you start Word unless you have the backstage open when you start (I start with a blank document). So, this has to do with why is Word automatically starting when you start your computer. It has nothing to do with any Auto macros in Word. It has nothing to do with any Word Add-Ins.
Your answer may vary depending on the version of Windows you are using.
In Windows 11, I would investigate my Startup Apps settings.
Since this is more a Windows question than a Word question, you might get better help asking in a Windows forum.