How can i fix my renault clio Immoboliser?

My clio works fine a lot of the time but now and again I have to sit inside the car for up to ten minutes locking and unlocking the doors with the key fob to get the immoboliser to stop flashing and let the car start. It always starts eventually. But as youcan imagine it's highly annoying if you need to get somewhere in a hurry.
Any suggestions? Any help much appreciated.
Rosemary