Screech through radio!

Hello everyone,
I am perplexed! Whenever its really cold outside, like under 15 Farenheit, and I startup the car with the radio on, I get an unbelievably loud screech through the radio. Funny thing is that the screech volume gets lower when I start accelerating. When I slow down the screech becomes louder again. Even stranger is that as the car warms up, the screeching goes away. Usually about 2 minutes or so. If I turn off the radio, naturally it goes away. I have checked the diagnostic mode on the MFD for any error codes and there are none. I have cleared the codes, rechecked and nothing.

Any ideas? Please help!!! Other than installing the factory OEM Toyota navigation system in my car, there are no other modifications. Oh and it did it once last year, long before I installed the Navigation system in it, in case anyone was wondering.