Restarts one time on every boot up - asus optimal mode

Hello  

Some months ago I built my first homebuilt and everything seems to be working great, though I have one problem..

When I enter BIOS and it's on 'asus optimal'-mode, then everytime I boot up my computer, it will restart once before it reaches the windows logon screen, and then it will boot up normally.  
However this does not happen when its on 'normal'-mode. But when it's on 'normal'-mode the computer only uses 1333 mhz RAM   and the processor is weaker aswell.
Though I've figured out how to change the RAM to 1600 mhz again.

This is the modes I'm talking about: http://techinstyle.tv/wp-content/uploads/2011/01/ez-mod... (not my picture, just a random from the internet)

But does anyone know why I keep getting this one restart everytime I boot in the optimal mode?
I know it would be better just to OC myself, but I'm not really sure how to get a good stable OC and all.

You can see my system spec here:

Intel Core™ i5 Quad Processor i5-2500K 3,3GHz
ASUS P8P67 PRO
MSI GeForce GTX 580
Noctua NH-U12P SE2 CPU
Corsair XMS3 DDR3 1600MHz 4GB CL7 Kit w/2x 2GB XMS3 modules, CL7-8-7-20, 1.65V
Corsair TX 950W PSU

Cheers
Patrick