Radio problem

[doublepe]

Hi,
I've got berlingo multispace desire 53 reg, 1.9d.
My radio started to be funny and turns the volume down to 0 by itself.
If I try to turn it up you can see on dash display that volume goes up and down like there was volume down pushed all the time. Funnily enough it starts to play normally when it wants and then plays with me again.
Sometimes works normally with no problems at all, and the other time it just turn the volume down and I can do anything about it?
Anyone any ideas?
Cheers
Peter