After Over clocking, P.C starts, stops for a second and then powers on as normal

Hi all, I have a question concerning my recent Overclocking experience and would be extremely grateful if anybody could help me.

My PC Specs are as follows: Intel Q660 C.P.U, 4 GB XMS2 DDR 2 800 Ram, 1000W P.S.U, Asus P5Q Pro Mobo, 500GB HDD, 3870 x2, Artic Cooling, 2 x side mounted fans, 1 frontal fan and one rear extractor fan.

I recently used the A.I Tweaker in the Bios of my Mobo to mildly clock the C.P.U to 2.7. I locked the Vcore at 1.25, set the Ram Voltage to 1.9V, set the C.P.U F.S.B at 300, with the multiplier set at 9, I tweaked the Ram to a frequency of 601MHZ. I left the Ram timings alone as I have no experience in that particular field. Some settings on the Bios have been left on Auto and the P.C.I Frequency has been left at 100.

The P.C runs absolutely fine when its on, with no discernible performance hiccups or any other problems. The only thing that concerns me is whenever I turn the P.C on, it starts up with the fans noticeably coming on, only for it to turn off for a split second and then restart. After restarting it continues with no other problems.

What do you think could be causing this to happen? Is it something to worry about? And is there anything I could do to counter the issue?

Sorry if my knowledge isn't the best as I am fairly newish to Over clocking. Any help would be deeply appreciated!