This is something that has just started this week. When I start the engine from cold, I can hear a quiet ticking noise from the area around the speedo, its like a clock ticking but more like 2 second intervals.
It doesn't make the noise with the ignition on, the engine has to be running but will still make it when the car is stationary.
After a few miles, it stops but will start again when the engine is stopped and re-started. Its not loud, in fact you really have to listen for it above the sound of the engine. It would be interesting to know what it is.
I did think of the fuel pump but I heard this ticking once before when it was getting very low on fuel but this was much faster and louder ticking.
Assuming it's NOT the fuel pump (which is a very obvious ticking noise - test by taking the wire off!) then I can only assume it's the voltage stabiliser which is in beside the speedo - and works woth a bi-metallic strip which makes and breaks constantly to give an 'appoximate' 10 volt output.
I had a poke about today in the daylight and it is the fuel pump. I noticed that after the engine has ran for a while the ticking interval increases to around 10 seconds - still very quiet though.