Delay in booting pc after power button press : Solved

 Recently observed that a long pause or delay of up to 30 to 60 seconds to show the boot menu on my home built PC after the power button pressed. There are solution of replacing the button cell in the motherboard and changing the PSU of the system. 

Then I came across another post suggested that to remove any additional USB devices connected to the PC except the keyboard and mouse. Then I remembered, few days back I inserted an USB pen drive but not removed from the PC after the copying was done.

After removed the USB Pen Drive, the system boots normally.

What happened? In the boot sequence the USB drive is added on top, so that in case of any system issue, the boot can happen from USB drive. Since, the USB drive attached to copy some files and not removed from the system, every time when the system is started it looking for bootable USB drive. Once the bios found the USB device is not bootable it is back to the HDD for system boot. This caused the delay in booting.

Hope this information will help some one facing similar issue.