Dell laptop Blank Screen

i have a dell latitude 5530 laptop. it is behaving un predictably. sometimes it boot sometimes it wont. when i push the start button. it simply give me blank screen. i can hear running hard disk and power button is on but still nothing on the display.
i tried to remove the battery and then hold power button for 60 sec. but it did not work for me.
how can i resolve this problem.