Would it be a pre MY2008 car?
For MY2008 onwards, pressing the start button initiates a starting sequence where the starter motor will turn until either the engine starts or you press the button again. After a poke of the button you do not need to keep it pressed.
Prior to that model you had to press the start button until the engine fires - if you took your finger off the button without the engine firing, the starter motor stops.
In the instance you quote, what probably happened is that the poke of the start button got the engine to fire but wasn't long enough to carry it over top-dead-centre. What then happens is that the engine oscillates backwards and forwards, firing on compression but not rotating.
Longer press next time.