Noise after turning off the engine – normal?

Hello to each other, I have already used the SF of MT and Google, but found nothing comparable to what my XC90 deals with the D5. I hope you can help. The following I noticed last time and I just want to make sure that this is okay, or I prefer to go to a workshop, as long as I still have a one-year used car warranty: When I turn off the engine, I hear something (metallic noise) going on in the engine room until it finally comes to a standstill. But that’s only heard when I open the door or stand outside. In the vehicle itself you don’t notice anything. Also, I sometimes feel that it is so “normally” . Could it possibly be the turbocharger that is still spinning a few more revolutions? I’m aware that a remote diagnosis is difficult. Well, since it’s my first Volvo I just wanted to know if it’s “normally” or not. Could it be the turbocharger that I can’t confirm that it’s still a few more revolutions going on?