Corebook pro laptop fan problem

Hello. i bought corebook-pro i3 laptop, the fan noise is ok in standart usage. when i start to use some web page, the temperture of the cpu is increasing a little bit, at that time, the cpu fun speed is increasing as well, but the problem is, the fan cannot speed up, 3 seconds later its speed decreasing, and this goes on,

if cpu temperture is hight, the fan speed is high, that is ok. but if cpu temperture not so high, the fan speds up, speeds down, speeds up, speeds down in 3 seconds cycle untill temperture drop.

i have windows 10 home.