Iphone reduces background music volume by it's own

So I'm facing an issue that the music(Spotify or apple music) reduces to extremely low level or sometimes just lowers once I unlock my phone XS with face id (not talking about the phone ringer). It doesn’t happen every time I unlock my phone after many attempts I encounter the reduction in music problem and this only happens in low battery percentage like below 30 having the Attention-Aware Features toggled off.(note: the Iphone is not connected to any bluetooth device i.e the audio is coming directly from its speakers.).Is anyone encountering the same problem?