CPU running up to 100%

Hello all,

Just let me start off by saying I am VERY new to WP and have almost duck all Linux knowledge. I deal with DNN sites in a Windows environment.

I have a customer that has a quite a busy site, https://www.fishingec.com, that I host and run on a dedicated server with a PLESK hosting front end. The average page view for the site is 1,547 per day

The problem is that about 8 to 10 times a day, the CPU hits 100% all that my hosting administrator does is restart the HTTP service and then the CPU usage goes back to normal, because this became such a frequent occurrence, he has since written a script that monotors the CPU usage and restarts the service as necessary.

These are plugin’s were are using.
Akismet
Content Slide Plugin
Google Analyticator
Image Widget
NextGEN Gallery
SFC – Connect Widget
SFC – Login
SFC – Register
Sidebar Login
Simple:Press
Simple Ads Manager
Simple Facebook Connect – Base
TDO Mini Forms
WordPress.com Stats
WP-Mail-SMTP
WP-PageNavi
WP-Polls
WP-PostViews
WP-UserOnline
WP Hide Dashboard
wp image slideshow
WP Wall

Can someone please offer a little advice as to what could be the problem with this and where should I be looking to try an figure out what is causing this problem.