Start up is kinda weird....Help!

Ok i have a MSI KT333 Ultra and when i turn the computer off and start it back up (no a restart) it will Sometimes* start to boot up quckly shut down start up again and start to beep and give no video. Its weird because the graphics card is in perfectly and so is the memory. It bugs me because some times it chooses to boot up fine and sometimes it doesnt... Please help any input is helpful.

WELCOME TO THE FORUMS

Is your board overclocked? What is your current power supply?

No its not, my graphics card was though...

What is the brand and model of your current power supply?

its an enermax 350 wattt supply. Ok heres some new news. Ok i can start the machine after its been not on for a while so if my computers on ill turn it on and wont be able to turn it back on ( i get a series of beeps when i turn it on) then ill leave off for about a while and turn it back on and its good. Is it my power supply? THanks