Game crashes randomly whenever I am in a world, It usually crashes within a minute.

Put the summary of the bug you're having here

What I expected to happen was...:
I thought I could log into the game normally and play.

What actually happened was...:
The game crashed shortly after I logged onto my server. I then went into singleplayer and it did the same thing. It has never done this before and I can no longer play without it crashing within a minute.

Steps to Reproduce:
1. Log into minecraft
2. Select world/server
3. Crash.