Common 'issue' (not really a problem, more an annoyance). What's worse is driving an non-synchro truck or tractor gear box when it's cold.
If you can't stand it, try double clutching when the box is cold. Google double clutching if you need to.
If it's a really bad problem, first replace the gearbox oil, make sure you use the correct viscosity, if that doesn't help replace the synchros.