When I first turn on minecraft, my computer is quiet then after about 1 minute my computer runs fast. I can hear the fan running fast and it slows down a bit and stays like that until i close minecraft. Is there a way I could improve this? I installed optifine which is optimine and optifog.

Here is my Comp Specs

Processor Name: Intel Core i5
Processor Speed: 2.3 GHz
Number of Processors: 1
Total Number of Cores: 2
L2 Cache (per Core): 256 KB
L3 Cache: 3 MB
Memory: 4 GB