iPhone listens to music but the screen is still bright

Hello,
I have a problem to solve and would like to ask for help.
While I was driving (Renault Scenic IV) and listening to music from my iPhone via R-Link, I noticed that the iPhone's screen continued to light up.
Even if I turn it off with the right button, the screen turns back on automatically.
Does anyone know the cause and how to fix it?
Thank you."