Need help ASAP please

I just buy components to build a new computer as a gift for christmas, I buy the mainboard ABIT IB9, after building the computer and turned it on, I was surprised from this wear problem. the computer turn on for one second then automatically turn off for about five seconds and then torn on again and then works just fine...
when I ask the about it on the store where I bought it they say it is normal and this mainboard operates in this way!!!!
I am afraid they are lying, so please can anyone help me, is it really normal or I have a defected mainboard?
I must know ASAP because I will give this computer for my Niece as a christmas present
help