My car does not idle after being started.
The fuel pump could be the source of your concern. If the fuel pump is weak or failing it won’t be able to provide enough fuel at idle and the vehicle will die unless more gas is added by feathering the gas pedal. The vehicle may run while driving because at a higher rpm the fuel pump can put out enough fuel, as where at idle the fuel flow isn’t enough. A proper diagnostic should be carried out by a qualified technician in order to find the true cause of your concern, and replace your fuel pump if needed.