When I login in to minecraft and start playing on one fo my worlds it will play for a few minutes then it takes me back to the launcher sreen

Put the summary of the bug you're having here

What I expected to happen was...:
i thought it would play like normal

What actually happened was...:
it plays for a few minutes does not load my skin and crashs

Steps to Reproduce:
1. play for a few minutes then it just crashed.