A51 randomly asks for password

I bought an Xfinity Mobile Galaxy A51 at the end of May. Generally it's been great, but it's doing something weird and inconvenient. I have it set up for fingerprint reading, but it sporadically requires me to enter my password. This is not after a shut down, which would be expected. In fact, it happens even when I've unlocked the phone to check messages or weather and put it down only minutes prior.  This is very irritating when I want to access my phone in a hurry and I'd like it to stop.