I partially agree with @F430. Its the coolatn flow noise from the radiator to the engine. When you start the car, its water pump starts with the timming belt or without the timming belt depending on the model.
1) Water pump pushes the coolant from the radiator to the engine to the heater core and back to the radiator. Initially you can hear the coolant noise when the car is cold, but it will go away as the engine warms up.
2) Some times you can also hear it form the heater core area. Newer cars have coolant flowing through the heater core at all times.
*Its not the fuel flow noise. You can not hear it.
*You don't have to worry its normal.
No worry dude...thast not a problem at all...thats the coolant flow from radiator to the engine wich takes motion from a halt as a cold car iz started...my city also did the same when it was new...now it doesnt do that....dont worry be happy...