problem with radio in 55 reg Nissan Micra?

I have a problem with radio in my 55 reg Nissan Micra sport plus , when driving along the radio goes off but this problem also happened when we had below freezing temps, it came back on once by itself , but as soon as the temp dropped again its gone off and hasnt come back on since and that was about 1-2 months ago .............PLEASE HELP!