My computer don't restart itself.

Hello,
I have a computer compaq presario V3000. My problem are, if i'm going to restart my computer it will not start my itself, all the lights are illuminating but the screen still black nothing happend. So I switch off manually and wait for about ten sec to switch on, sometimes it start but of the time it did, unless i'm going to get the battery out then ,it work.. I can switch on my computer. But it happend that, I'm going to switch on and off for 2 to 3 times before it work, with out the battery.
Will you please help me to solve this problem