you should check the logs and why this issue occurs
http://wiki.centos-webpanel.com/service-log-pathsalso this could mean that your server phpmyadmin is under bruteforce attack or you simply have some issue but I would suspect on bruteforce attack since this issue occurs only for phpmyadmin.
you use this command that you don't need to restart your server
sh /scripts/restart_cwpsrv
but you should check the logs before