PHP and MYSQL

Hi all, I have a form where I collect some information and then that information is saved on a local db (mysql). The problem that I'm having is that when the server is up an running for few hours and when a user clicks the send button, my page take a long time to communicate with my database and at the end, I get an e-mail from the output. But what's really strange is that if I reboot then server and try the page, everything works really fast and in matter of seconds I get my confirmation e-mail. I'm wondering if there are some settings that I can tweak on the server, OS or on the CMOS to avoid that kind of delay in my form. I'm guessing that probably after some time the server is going into sleep mode or something. I'm using PHP4.0 , mysql and apache. Thanks again for any information, -hb