What I'm hearing you say is that you cannot access your webserver, and you think it's because the hardware goes into sleep mode. To determine whether the hardware is asleep or the webserver process is down, I would ask the folloiwing questions:
1) Can you log into the server that apache is running on, even when you can't reach apache?
2) Have you looked at the running processes to see if the apache process is still running?
3) What do your apache logs say during the time you cannot reach the webserver?