Vauxhall Corsa hi, corsa d reluctant sometimes to start on first crank but always starts on second crank. car runs perfectly with no faults detected on obd scanner.

Few months ago car started having problems starting . Began to hesitate on first crank but then always would start on second go. Car crank is good so plenty of power . Ignition system ok -had new coil pack, crank shaft sensor , coolant temp sensor , fitted. earth connections checked , fuel pump checked but problem still there . Car runs perfectly with no codes showing up on obd scanner .