Does it happen when you turn off the HVAC first and then turn off the ignition? If so it could be a HVAC pulley tensioner. If it occurs even with HVAC turned off, it's likely the Alternator/Serpentine Tensioner..
if the vehicle is under 48K miles it should be covered under Warranty.

 

The noise at startup could be the high pressure fuel pump, it is a cam driven plunger. It is normal to hear the high pressure fuel pump noise. The noise turning off the engine could be the cam seals behind the timing belt end of the engine. The seals make a noise all the time. You only hear it because the other engine noises have quieted down as the engine is rotating to a stop. Volvo has been replacing with updated cam seals. You should get a new timing belt kit installed with the cam seal repair. This is for new B5/6 engines, 2022-. Also look under your car to the inside area of the right front tire. The new engine has an external belt driven water pump. Some of pump seals are leaking coolant. I do not know if there is a VIN range break for the cam seal noise.

 

You should get a new timing belt kit installed with the cam seal repair. This is for new B5/6 engines, 2022-. Also look under your car to the inside area of the right front tire. The new engine has an external belt driven water pump. Some of pump seals are leaking coolant. I do not know if there is a VIN range break for the cam seal noise.

Just had the car in this morning to get it looked at. They're changing the cam seals. I asked and was told they're not replacing the timing belt.

 

Ya there is a TJ for that squeal from cam seals when shutting off.
The fuel line/ high pressure pump is a super loud ass metallic rattling noise you cant miss

 

Hello. Did you ever get this sorted? Mine has just started doing the same. Cheers!