Mysql stops working automatically in Ubuntu 14 server

Some times my site gives a error "Data base connection error". After i restart the server (Sudo reboot), then everything works fine.

At-least once in a week i get this issue. I can't monitor over this site always. Need to know the exact reason and solution to solve this problem.

Site details:
www.kinindia.net build with wordpress and hosted in Ubuntu 14

Have you checked the log files (in /var/log/) for clues?

Yes, but i can't understand it

As a starting point, I would look for log messages that contain "mysql" and seem to indicate errors.