iPhone SE Mutes volume automatically?

Hi all! Haven't been interacting with y'all for some time, hope you are all doing great.
I've had this strange issue with my SE for two or three days now, running iOS12.1. I'm writing to ask if other SE users have the same issue, where using the phone's speaker to listen to VoiceOver speech, without me expecting it, the phone automatically sets the volume to 0%. The only way to break it off is to adjust the volume manually to make VoiceOver come back again. Restarting the phone doesn't work.
I'm trying to determine if this is a bug within the system, or a hardware issue with my own phone. If it's the latter case, then I guess I need to take my 2-year-old phone to the store to have a look or something.
Thanks for reading and see you next time!