problem with FPS

Hello guys =)

I have some problem with my FPS.
When i join a server i have fps lagg for the first 3 minutes. It goes like this: 125>>114>125>>112>>125>>118. After +- 3 minutes my fps are pretty stable 125.
PRETTY, because it jumps from 125 to 122/123/120 sometimes, that's really annoying me. I just want a stable 125.0
It's not my pc tought. Someone knows how to fix this?? (MAYBE O'CLOCK MY CPU?)


PC specs;

CPU: Intel i7 920 @ 2,67GHz
Graphics: Clubd3hd HD5770 OC
Memory: 6GB DDR3 1600 memory (3x2GB)

comments plz ;]