Radio play interrupted by "talking..." mode - how to stop that?

Frequently (though not consistently) when I'm listening to the radio the radio sound cuts off and the dash reads "talking...." as if it's waiting to either talk to me or for me to talk to the system. This interruption is unwanted. I'm not doing anything to interact with or request any function - I'm just listening to the radio. I can get the radio back by pressing the "call hang up" button my my steering wheel, but it happens again and again. The only way to stop it is to turn off bluetooth on my iphone. Help?

 

Not sure why the question about a 2001 - a typo? This issue is in my 2010 which does have voice activation.