Will only boot up 50% of the time during a restart

[Zenara25]

I put together a computer. Bought over ebay a used Epox 8K7a motherboard. Asus Geforce 2 MX 200 64mb video card. 2 sticks of Kingston PC2100 256mb(total of 512), 2 40gb hard drives, 350 watt power supply, athlon xp 1700, dual boot windows 95 and xp home,cdrom drive, and floppy.

Didn't notice the problem til I had to restart computer after installing programs.

Bios is up to date.

Any ideas on why my monitor shows nothing on restarting. It looks like the computer is working fine (I think)just nothing shows on the monitor. Then I shut it off all the way and press the power on button and it works fine.

[nukes]

Is this when it reboots, or any time you turn it on?
Am I right in thinking all the lights come on, hard disks and fans spin up etc. Just nothing actually happens. Then if you power cycle it or press the reset button it works?
If this is the case, check 2 things:
1. power supply. (doubt this is the problem)
2. How many plugs are in the one socket? Are you using a multi-plug extension lead or something?
If so, plug the base unit into a plug socket on its own and see if that helps (has helped me before)
Also, as you bought the mobo on ebay, it may be faulty. Not really sure where you can start to test this though.