Twice this week I have gone out to the garage and witnessed a strange noise coming from the rear of the car. The car had been parked, locked and not running yet witnessed a sound similar to that of the hum of an electric motor. Using the lock or unlock on the key fob had no effect, The first time I started the car and noise stopped when turned off, The second time I did not start the car, but switched the ignition to the Run position then turned off which stopped the noise.
Does anyone know what this is / is it normal / how often and how long does this run?

 

sounds like the fuel pump to me.

 

This?
Page 6 in the manual.