I recommend that you install the software packages munin and monit on your system to monitor the server parameters. You can find tutorials for that here on howtoforge.
Additionally you should check your apache access log if there are any unusual requests. Such a high load can e.g. be caused by a DOS. Then enable also the slow query log in mysql as slow mysql queries can bring down apache as well.
It is unlikely that the problem is directly related to ispcnfig.