Dashboard hangs; forces apache restart
You are experiencing CRM-16035 - Dashlet refresh can crash server.

The default dashboard config is pretty close to maxing out the default Debian config for either Apache or PHP-FPM.

Depending on your server setup (question says just Apache which typically suggests via mod_php) you probably need to increase either the number of  connections Apache permits. 

You could also remove some dashboard widgets for the affected contact - if the dashboard is currently inaccessible so not editable for you, you could do this by directly editing entries in civicrm_dashboard_contact in the DB.

If you are using Apache + php-fpm or fcgi, you might need to increase the max_children setting in your php-fpm config instead. For non-Apache users, other StackExchange will explain how to increase server limits for your php/webserver configuration.