how can I fix gearbox mazda 323 1999 auto?

in the morning or after the car has'nt started for a non very long period,when I put in D or in any other gear for that matter,the car do not go in gear and does not move.It's like if still on Neutral or Park mode.I have to wait up to 3 mins before it goesand after that runs as nornal as nothin's wrong with it.please note that last serviced 6000 km ago I changed lubricant and filter in the thr gearbox but it did not improve at all