Please refrain from stating comments in all caps.
As has been previously stated, there are many things that can cause a website's performance to suffer. This can be anything from large log files and databases in severe need of optimization to other issues that would only affect a single website/account/database/etc.
A good place to start would be to use the
top command to determine which processes may be hogging CPU. If it is MySQL, then this thread may be helpful:
http://forums.cpanel.net/showthread.php?t=74265
That's a starting point. There are *many* things it could be and without root access to the server it would be hard to properly diagnose the cause of the issue. You may wish to have an experienced system administrator (or a company that offers such services) look into this for you.