I have a CentOS server setup that currently hosts several websites (all relative of each other in some form or another). As of recently throughout the day at the most random times the website speed will lag to a crawl and eventually hit a connection timeout. When I say random times this typically happens anywhere between 10am and 1pm usually, however, this morning this happened to me at 8am.

I do not have a lot of familiarity with server knowledge as far as what I am looking for in this situation. What are some possible causes of why my server is slowing the websites down to a complete crawl or timing out?

Are there specific things I should be checking for when this happens?

I have noticed using:

tail /var/log/httpd/access_log

That usually when this down time occurs there are lot of IP addresses related to BingBot, Googlebot, and sometimes various bots or spiders that I am unfamiliar with. Could this be related and if so how can I avoid this from causing my websites to lag out?

Thanks in advance for any help or advice. The websites that are timing out are built with PHP and use a MySQL database to display information.