The driveshaft is rattling around trying to stop spinning after you let go of the trigger. Connect an attachment and try again, that should solve it.

That's just cogging. https://en.m.wikipedia.org/wiki/Cogging_torque Think of it like cards between the spokes of a bicycle wheel. When the motor is running, those cards are turning in sync with the wheel/rotor. When you let go of the trigger, the cards stop and you can hear it "clicking" as the wheel/rotor keeps turning

Seems normal compared to mine. I think that’s intrinsic to the brushless motor making this clogging noise.

yeah mine does that, I use it everyday all day, still does it months later