Display is Freezing up after a few minutes

Hi.

I have a apple iBook G4 Model No A1054 it's freezing up after a few mins from booting up and some times just goes to a blue screen then you have to wait about 20 mins before booting up again i've tried holding down various keys on start up with no luck !!

And taking out the battery and holding the power button down with no luck.

I've also noticed that the little light on the front is not lighting up when it's in sleep mode. it's had a new battery and a new charger

can any one HELP me please .

Regards Daz.