Booting up issue of omnibus f4 sd

I dont have much experience with this
most of the time the stm32f4 is booting in to the
Dfu mode

If i connect multiple time by the usb after some
attempts the blue led blinks and every thing works

If i turned off the board and powerd on next day i need to reconnect multiple time to work

Is it button issue i dont have a hot gun
How i fix it