Loud Humming When First Truning On The Pc

Two minutes, that's quite long time then. It's also possible that fan causes case to resonate. Easy to check, when hearing that noise, put your hand on case. If noise is different, then it's probably resonation. If not, then probably fan is indeed getting broken.
 
Fan(s) may be a bit broken. Works fine some time, some time not so fine. Wait until that noise happens again and see what fan is noisy.
 
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