By default, the lifetime of the session in a new installation of PhpMyAdmin and ‘cookie’ authorization method is 1440 seconds (24 minutes). Which means that after 24 minutes of inactivity any action brings the user to the login page. To increase the lifetime of the session, you must set the variable
$cfg['LoginCookieValidity'] = 1440 * 60; // 86400 means one day (24-hours)
, say, 60 times. That amount per day.