My galaxy S9 constantly shuts off after I lock it. I have read on several forums that the problem is fixed by disabeling the fingerprint lock. However, when I go to disable it (Settins > Lock Screen > Finger print > Enter code) and get to the enter code page it shuts off again! It is so annoying I don't know what to do.
I would recommend testing your device in safe mode to see if you continue to experience these symptoms. If your phone is misbehaving, it's possible that a third-party app is causing the issue. To figure out what app is acting funny, you can use the Safe Mode feature. In Safe Mode, your phone won't run any third-party apps. This allows you to easily identity and remove the app that may be causing the problem. Give this link a try to see if you are able to disable the fingerprint: https://www.samsung.com/us/support/answer/ANS00062983/
Next step would be to wipe the cache partition on your device: The system cache partition stores temporary system data. It's supposed to allow the system to access apps more quickly and efficiently, but sometimes things get cluttered and outdated, so a periodic cache clearing can help make the system run more smoothly. Give these steps a try: