Is the speed "inconsistent" as in sometimes a specific page is fast and sometimes it's slow? Or are the same elements always slow? Perhaps you've already done this, but run the front-end through some tests on Pingdom first: http://tools.pingdom.com/fpt/ That's where I'd start if it was one of my client sites. From there I'd run the P3 plugin to see if there was a specific plugin causing any issues (https://wordpress.org/plugins/p3-profiler/). I have a few other things I check for but these first two are easy enough for a non-tech to at least get started.