Do you have open tabs? Does Opera freeze after a few seconds upon every startup ("not responding") and stay unresponsive so you have to force-close it? If so, that sounds much like my problem. Here's how I solved it:
Exit Opera (force-close) Back up the file "Current Session" from your profile folder: https://help.opera.com/en/latest/crashes-and-issues/Alternatively, just back up the whole profile folder (C:\Users[UserName]\AppData\Roaming\Opera Software\Opera Stable). Delete the file "Current Session" from your profile folder. Start Opera. (It should work fine now but your open tabs will be gone.) Close Opera. Copy your backup of "Current Session" back to your profile folder (replace the new file Opera created automatically). Start Opera. Success!
If you don't need to keep/restore your open tabs just follow steps 1, 3 & 4.