Mac start-up problems

[Oyvoyvoyv]

My friend has been having some issues with his mac book not starting.

If he presses the start up button, the screen goes blank for a few seconds, before it says that it needs to be restarted.

The same repeats if he does it again.

We've tried checking around to find the problem, but it seems impossbiel to find anything. Might call the support line, but that isn't free, so would prefer to not have to do that.

So I have no clue how to fix it really, and was wondering if anyone could give a little help.

It would have to be told pretty basic though, as I'm completeely retarded when it comes to Macs.

Thanks in advance.