Hi,
This could be due to corrupt Store settings. Third party security might also cause such issues while using or downloading apps from Store.
I would suggest you to run the app troubleshooter and check if it resolves the issue. Follow the methods:
Method 1:
Refer to the link to download and run the troubleshooter:
http://download.microsoft.com/download/F/2/4/F24D0C03-4181-4E5B-A23B-5C3A6B5974E3/apps.diagcab
Restart the computer and check if you still find the Store popping up on startup. If yes, proceed to the next method.
Method 2:
Let’s re-register the Store and check for the status of this issue. Refer to the link:
http://blogs.msdn.com/b/notime/archive/2013/10/18/fix-store-app-in-windows-8-1.aspx
Note: This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow
these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, you can refer to the following steps to back
the registry files on the computer:
a) PressWindows and R key to open the run box.
b) Type‘regedit’ and press Enter from the keyboard.
c) Open thefile option on the menu bar.
d) Click onExport and save the file with a name on the desktop.
If you want to restore the file, you can do so by double clicking the file that you have saved on the desktop.
Method 3:
To check if the issue could occur due to the antivirus, I would suggest you to temporarily disable the Norton security software and check if it resolves the issue.
Important Note: Security software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable
it to install other software, you should re-enable it as soon as you're done. If you're connected to the Internet or a network while your antivirus software is disabled, your computer is vulnerable to attacks.
For further reference, you can also refer to the link and troubleshoot issues with other apps apart from Store:
You may check if there are pending updates for the Store. You can uninstall and reinstall the apps from Your app section in Store to troubleshoot such issues;
http://windows.microsoft.com/en-us/windows-8/what-troubleshoot-problems-app
Please let us know if the issue still persists. We will be glad to assist you further.