Does the same issue also occur in an Incognito window (Ctrl+Shift+N)? If it doesn't, check your extensions that are installed and enabled,, try disabling your extensions one by one to find out which one is causing the pop up and Make sure that there are none there that may be causing the issue,
Try resetting your browser settings to see if it helps. To do so, check here - Reset Browser Settings.
Check for malwares. ( Try downloading CCT or You can download malwarebytes to remove unwanted programs