G4 power cut out problem

Hi, I'm new on here so please be gentle. I have an old G4 Tower and in the last week it has repeatedly switched itself off after five minutes of use. I'm not very technical and so have no idea why this is happening. Any clues?
Thanks.

How hot is the system getting before it shut off?

Download MenuTemperature for Mac - CPU temp monitor for G4/G5/Intel machines. MacUpdate Mac Software Downloads

It might be shutting off because of a heat or cooling problem. Are all the fans working properly?

G'day and welcome to the forums.

And scooter how long since you opened her up and gave a really good and thorough clean? Dust is the enemy of all computers, and in particular to the Morror Drive Door (MDD) G4 models.

Pay attention in particular to the inlet, fans, hard drives, graphic card and outlets. Also does the graphics card have a fun and is it actually working?