Kinda strange

This never happened before but today when I turn my Sony notebook I noticed the fan was on full power right away even the room was around 68F.
But when I when to standby mode then of cource the fan turned off then when I wake the computer the fan is working as normal.
I just wondered why did the fan use full power for more than 30 min after I turn on my computer this morning even the room was not hot at all or the computer.