sound like a narcoleptic PowerBook
this problem were pretty common on those aluminum g4 PowerBooks.
it's a defective temperature sensor right under the trackpad.
the best way to solve this, is to remove the sensor completely
you can read more about it [http://web.mac.com/rickcameron/iWeb/Electric%20Lamb/N.A.P./N.A.P..html|here (click me)]
the sensor is shown [http://s1.guide-images.ifixit.net/igi/RrYpL1yVeV6nD6qN.huge|here (click me)] - right between the two white connectors