Since you didn't mention any overclocking, etc, go into BIOS, load Optimized Defaults, manually set memory voltage and timings to match your memory specs, and save/exit. Remove or otherwise disable Gigabyte's OCing utilities.
See if the symptoms disappear.
Then slowly add back any timing changes you (or ET6/Smart6) made.
It's having a problem with hardware during post - It could just be a race condition, it's checking a parameter before it has stablized. For your memory, Set memory to Use profile 1, that should set memory to factory specs.
As for memory, I use memtest before loading the operating system, and if I make any changes affecting memory I use a boot CD with memtest. But I find prime 95 much better at identifing memory errors.
How's your PSU. Is it a "good" one and are the Voltages good.
But once started no problem at all.Its stable no fluctuation etc. Even when I restart - no problem. Always the first time only!
Your mobo either needs to change some parameter the first time through, or at least needs to try twice to start up from cold. It does one of those, and everything is fine.
Usually this is memory (or psu) related, which is why Chief and I gave you two ways of ensuring memory settings match memory, using the settings that have the max chance of compatability. (You could try Fail-safe defaults, too)
Alternatively, it could be your psu is not providing adequate, clean power when first awakened. Like me, it may be a little slow getting out of bed in the morning lol. This 2007 review article: http://www.anandtech.com/show/2283/1
talks about lower than desired voltage levels and software to tune the rails. I don't know if that is connected to your issues, but its worth reading and thinking about.
Thank you for the concern..I removed all the ram bars and I am going for exchange with my stores. When I built my system 1 month before i got Kingmax 1600mhz ddr3 ram (2x2gb), which worked flawlessly.Only now I remember that there wasn't any beep when the system booted.. Last week only when I changed my ram to Kingston 4x2gb all these happened. I cleared cmos many times, loaded fail safe as well as optimised defaults and now i hear the beep when the system boots...I am not sure the absence of beep is normal or indicates something is wrong! Once booted no problem...10 min of PRIME 95 - ok no problem. Right now running on 1x2gb standby ram ..have to check after few hrs of switching off. May be the ram comes on wednesday...Suppose nothing works I am planning to go with kingmax 1600mhz - problem is I am planning to install Noctua NH-D14 - worried about the clearance from board....
I am glad to say that all my ram bars were exchanged at the stores and I got new set of 8GB which the recognised and now the system beeps(normally) during booting and no hiccups so far. Thank you all support!