Pluggable line 1207 error

Hey people,

Once in a while (few times a day) my sites goes randomly down and gives error:

Warning: Cannot modify header information – headers already sent by (output started at ../public_html/blog/wp-config.php:12) in ..//public_html/blog/wp-includes/pluggable.php on line 1207

If I refresh my site few times, it goes back up.
I’m running WordPress 4.3.1 running Independent Publisher theme.

Link to WP blog: http://bit.ly/svtearly

I’ve tried everything and even contacted the Hostgator. Do you guys have any suggestions, how to fix it?

Thanks so much!