My truck sits outside here in Colorado and starts and runs fine in the winter. The problem is the stock radio will not play at normal volume until it warms up. I can turn the volume knob up and the scale shows it at full volume but you can not here anything until the cabin warms up then it will gradually increase in volume until it is just fine. I know it is old but it is not a tube radio.
But is IS a broken radio.
If it was then some one put a pre 1960 radio in your vehicle.
Either replace radio or just live with the problem until it quits completely.