Steam downloading question?

I have steam and i am currently downloading a game, and for no reason at all, out of nowhere, the game pauses its download, and this isnt the first time it just mysteriously pauses. My internet connection is fine but sometimes it pauses on its own when i download it? And with games that take up to 6 hours to install i cant afford 10-20 minutes of pausing,lol. Why is it doing this?