Nissan Micra Radio goes silent on FM?

Can anyone help? My Nissan Micra radio works fine on LW and MW but when i try tuning into FM stations they play for about two seconds and then everything goes silent. If i switch the radio off and on again i get another couple of seconds of clear radio music/chat before silence returns. Save me from keep turning off/on every two seconds - it's very inconvenient!
Thanks
Paul D