Can't listen to FM Stations

Hi

I hope someone can help!

I have had a Sony CD Changer for 3 years and never had a problem until recently. When I listen to any FM radio stations the sound will suddenly disappear, I can turn the volume up a lot to hear it again but after a few minutes the sound will come back really loud.

I can listen to CDs without a problem and also any AM/MW radio stations, it is just the FM ones.

Can anyone recommend (in simple terms) what I should check first?