Win XP PRO boot stops

A few days ago I’ve started to have a problem when booting, everything looks normal but a few seconds after the black Windows XP goes away, instead of the light blue Windows screen while loading Windows, I get a blank screen, the LCD monitor looses its signal, power light goes to amber, mouse usb wireless receiver turns off and then nothing happen.
At this time I have to turn the computer manually off, wait for a couple of seconds and turn it back on again, this time it boots in normal way.
It’s been like this for a few days, it always boots well the second time.
I would appreciate any help with this.
Raul