My (factory) radio reception deteriorated over the last few months. AM now is pure static and only the strongest FM stations can be heard - with lousy fidelity. AM & FM work perfectly when the engine is off and the key is on “Accessory”. My Sirius radio plugs into the audio input on the faceplate and works fine with the engine on or off, as does the CD.
I remember having to put a capacity on my 1965 LeMans distributor cable to kill the static. I hope we’ve progressed since then!!
That was a capacitor.
My guess is that you have serious leakage going on somewher interfering with your reception. An '08 will have COP, but you could still have a coil with a cracked housing or even a bad ground somewhere.
Another possible source of radio interference could be the cables to the spark plugs. If the insulation on any of them is worn or cracked, they’d need to be replaced in any case. Inspect them in the dark with the engine running for any signs of arcing.
You have some type of ignition interference. You need to get the vehicle checked out.