PC Peripherals Case fan making noise

Hey everyone, ive had my build for a little over 2 years now. about 2 months ago, one of my 4 case fans started making a weird noise. the noise only occurs if the computer has been off, or standby, or sleeping for over 10 min. it happens during start up and keeps going for about 5-10 min and then it goes away. it is only on 1 of the fans. does it mean i need to replace the fan? maybe spray some wd-40 on it?
 
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