Posted 18 January 2012 - 06:44 PM
Before replacing the fan, look at the manual for your motherboard and see if it has special BIOS settings for the CPU fan. If it does, then you might find a solution there. For example, some motherboards have a feature for setting the CPU fan to quiet mode and I could see this causing a problem with a fan that is sticking slightly and gets a bigger kick of voltage when booting than it does when waking from sleep.
If you are uncomfortable with looking at your BIOS settings, I can tell you how to proceed safely.
Have you looked at the fan? If it has a wire or cable rubbing against it or has a lot of dust on it, that may cause it to be harder to start spinning when waking than when normally booting (the initial surge of voltage can be different).
If you open it up to look at the fan, be sure to turn it off, unplug it from the wall, push the power button to make sure any residual power is drained, touch the metal casing first (in case you have static electricity built up in your body) and use a pen or pencil to see how easily the fan spins.