My Dell Inspiron has trouble booting...

Hello,

My Dell has trouble booting, it keeps shutting itself down during the booting process. Sometimes, when I press the power button, i can hear the fan start, then the computer just shuts down. no display comes on or anything. This can happen sometimes over 10 times. Sometimes it gets to the startup screen then shuts down. So far it has eventually booted all the way up, after quite some time. Once it boots up it runs fine and never shuts down. Anyone know whats going on?