Had exactly these symptoms on a 1.4 Polo, could be temperature sensor which has 2 circuits; one for gauge and one for ECU. Cold starts aren't a problem as the sensors tells the ECU to richen the mix, hot starts the sensor 'sees' a cold engine and gives the ECU the wrong information and hence a poor start, this was always accompanied with a strong smell of fuel and was intermittent as the sensor didn't fail completely. The longer the engine was stopped the less likely the problem. Changed the sensor and cured the problem.
