Why intel cpu fan working ok after sometime in h61 motherboard

Fans need some time to start after pressing the power button!!

The fans maybe controlled by the temperature of the cpu. As it gets hotter, upon start up, it will slowly turn on as it adjust to the temperature.

That is the normal start up with the newer fans, they take ~ 3-5 seconds to "boot-up".
I believe it is part of the sensor checking for the positioning of the fan blades.