I presume you are going to the proper place in Settings to Enter a Pin or Pattern, maybe Face, or Fingerprint lock. I don't know the S8+.
Assuming you are, it sounds like a "flakey" possibly occurring after a software OTA update. Did you get one recently?
I recommend first, try a System Cache Wipe. This is not done from settings, but from the recovery menu. I don't think VZW has the steps on their site. Google it. You'll find it.
If that doesn't help, I'd backup my important content onto a PC, then I'd perform a Factory Device Reset (FDR).
If you use Samsung Pay or Android Pay, you can't turn off the lock screen completely until you remove the applications that require additional security.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.