If its an older computer 4yrs+ you may need to replace the M/Bs CMOS battery, its a rechargeable battery and although some can last quite awhile others don't, I usually replace mine every 2 years anyway, its a cheap solution to avoid trouble.
That may not even be your problem because resetting the computer doesn't reset the date and time, but another indication of CMOS battery failure is date and time incorrect, and the CMOS forgetting the boot setting parameters, and reverting to the default settings.
If you haven't had to reset the date and time then disregard this suggestion.
Did this suddenly start, or have you added any software, or hardware to the machine recently?
My date and time are correct. So,it is not the CMO battery.
STURM had suggested to replace the power supply. But how does the computer start ( if left off less than 5 min) without having to hit the Reset button. Please note that no new hardware has been installed lately.
sturm could be right it may be a power supply [P/S] problem, there could also be a host of other reasons it could be happening, his suggestion to swap out a P/S with a known good one is a good suggestion, because you can discover if the problem is solved by doing so.
But if you don't have that option and end up buying a replacement P/S, you also need to be taking into consideration, are we talking a name brand computer such as Dell, Gateway, HP, Compaq, Etc. which may take a specific replacement size and type of P/S, so what type computer do you actually have?
If the computer is over 3 years old, its a good possibility it very well could be a power supply problem, your local computer repair store will have a power supply tester to see if there is an output problem with the P/S and if it is, they can reccommend the replacement you need.
I have a similar problem:- when I first turn on my computer (cold) the fan comes on but nothing else happens (no beep, no monitor, no checks, just the p/s fan). Then I press the reset button and the computer beeps, the monitor activates and the checks start but freezes around about the pool data check screen display. I press the reset button and the computers advances pass the previous boot to the blank screen that precedes the Windows XP loading screen and then freezes. I press the reset button and the boot advances further, this time to the Windows loading screen and freezes. I press the reset button and it will usually (but not always) goes on to load Windows successfully, however it will often freeze after windows loads.
Each time I press the reset button and it will load further than the previous until, eventually, it completes the boot.
Once booted completely I can press the reset as many times as I like and it will always reboot completely, but if I close and try another cold start I have to go through the whole reset procedure again.