Please Help on Apache Optimization! Website Down!

Hi Everyone, This is Gey, who is a webmaster. I would like to seek answers to the below question: The Setup is: One of my website has 7,234 visitors per day, totaling about 75,327 page views. Average page size is about 3mb as it is an image heavy site. And the DB size is about 300mb. We have a VPS server with 8 CPU Core and 16GB Ram. The Issue is: The CPU usage keeps hitting 100% while Ram only uses 20%! When this happens, the website will be down so it happens too often that we really cannot stand! And this happens when concurrent users are only below 100 visitors! So there must be something wrongly configured with our Apache Configuration! But we have no idea about how to make it right... Can experts here please help???? BR, Gey