I have had strong FPS drops in Minecraft for a few weeks, they go from 400 fps every 5-20 seconds to 0 for 1-2 seconds, what could that be? Have you ever heard of RAM, is it the RAM or what could it be?
How much RAM do you have?
32gb
Before you play in a server go to the settings or play with a client or with optifine
Do you use an FPS Boost Client like LabyMod, LunarClient or Optifine?
What hardware did you use in your PC?
What version of Minecraft are you playing on?
I play with Lunar client on 1.8.9 :)