Restarting the database service is hardly ever necessary, and is not the way to resolve database issues. The most common cause for questions about database restarts are stuck queries.
Stuck and long running database queries
Stalled queries, or long-running queries can be managed in PhpMyAdmin by selecting the database, then Status > Processes.
The process list displays a list of the currently running queries, and can be refreshed with the "refresh" button. Database queries run in parallell, so there will usually be multiple queries running at the same time.
You can kill specific queries from this interface. The query will not be completed, but aborted and the query will return a fail response to your CMS, webapp or cron job.
When is the database server restarted?
Servebolt restarts database servers when the database service is upgraded, and the upgrade requires a service restart. The database service will also be restarted when the server is rebooted.