Intermittent speedometer and rev counter.

Hi.

I have a '96 Polo 1.0l which has an intermittent problem with the instrument panel. About half the time from start up the speedometer and rev counter do not work. I can tell if they are going to be faulty, as when I turn on the ignition, the rev counter will flicker continuously at rest. This will continue upon starting the engine and all through the journey. When it is ok, the rev counter will flicker for about a second, then stop. Upon starting the engine all will be fine. It doesn't seem to be temperature related, as it can happen when it is a hot or cold day. I replaced throttle cable recently and it started around this time, more or less, but nothing seems to be disconnected around the areas it runs by.

Many thanks