iphone 13 pro max sudden volume increase

Hi, I've had my 13 pro max for about 2-3 months now and in the last month it has started randomly increasing the volume to 100%. I first noticed it doing this while playing Pokémon unite, and I just thought maybe my case didn't fit quite right. Today, while using my phone as a timer for my workout it randomly increased the volume to 100% without me touching it. I've never experienced it doing this with wireless headphones, and it only does it once in a blue moon, but it is quite startling. Can anyone explain why it does this, and how to fix it? Just incase it's important, my software version is 15.1.1