My PC is behaving weird in a way that during a cold start,
after BIOS boots up, when the Windows logo appears the
monitor goes blank with the message "no input signal".

But, if I warm up my PC by entering the BIOS field & looking up
the temperature of the system. When the CPU is around 53C
and the system is at 40C, the PC normally boots up.

I would appreciate it very much if you could give me advice
regarding this.

Thanks.

System details
(I've been using this PC for more than 1 year without any
glitches)
CPU: Athlon XP2500
Memory: PC3200 512MB x 2
MB: WinFast K7NCR18G-ProII
Video card: ATI 9600 pro (Sapphire)
DVD-1: Combo Lite-on LTC-4816H
DVD-2: Pioneer DVR-108
HDD-1: 80GB Seagate ST380011A
HDD-2: 250GB Maxtor
PSU: 450W (12V : 25A)