Screen Lag

Put the summary of the bug you're having here
The game lagged every once in a while until it crashed
What I expected to happen was...:
The screen would keep lagging without crashing.

What actually happened was...:
The game dropped to 0 fps every minute then after a few minutes it crashed.

Steps to Reproduce:
1. Start minecraft
2. Enter a world.
3. Play for a while
4. See if it goes down to 0 fps every once in a while.

Might be a problem in my computer.
Sorry for bad english.