Hi Melissa,
It is actually pretty common for wp based sites to spin out repeated 404 errors (or at least have the potential to do this). It could be a theme issue, a plugin issue or a setup issue or a combination of all 3 depending on the site.
First thing to do is figure out where the link is coming from. Download your moz error report in csv and filter by 404's. On the left you will have the 404 page and on the far right you will have the referring page. Go to the referring page and view the source and try to find that link. Keep an eye out for relative links from deep structure pages also (so you have page /category/page/5 and the link is a relative href="/" or href="/6" which can have the effect of spawning repeated 404s like /category/page/5/6 etc etc).
Once you have found the link, you should be able to identify the template part which is producing them and then act accordingly to either edit the template or adjust the settings/plugin so that they stop. If you can give us a real example of a 404 and its linking page we should be able to give you more specific info.