httpd processes

[<go...@go...>]

On my server, several clients have their own webmin account and use it with
https enabled. Sometimes, the httpd processes go from about 9 processes up
to about 50 and more. The websites on the server then don't response
anymore. I have to restart httpd and everything is fine again. This happens
about 1 to 2 times a month.

Is this possibly somehow webmin related? Would it be a good idea, to restart
httpd every hour by cron?