You probably installed some application/extension that have changed your startup Google Chrome tab.
You can change Google Chrome startup behavior in Google Chrome settings.
Open Google Chrome and, on the right of top bar, you can see an hamburger menu or 3-dot menu. Click on it and select Settings.
You should see On startup section as showed below:
Click on Set pages, from popup that it will open remove unwishied tab and add your preferred website.
For example I use google as startup tab.
If this not work you could try to watch if there is strange extensions installed on your browser. To do this in Chrome type this in search bar:
And look at your extensions. If there is something that you haven't installed, uninstall it.