eZ Publish provides a lot of cache stuff to make your web works like a charm. It could be extremely slow if you don't use them.
At a first try i would try to see TemplateCache and ViewCache. If those settings are enabled, (i think they come like that by default) check also permissions for your [document_root]/var folder. User running webserver (www-data in debian based versions) should have the rights to write in that folder. If not, no cache will be generated...
After that, enable site.ini\[DebugSettings] debug ouput (see settings/site.ini for settings doc), either by ip or by user id to be able to see how many database calls you have pr page and such.
If you have more then 5 then you need to look into your cache-block use and other stuff, if you have more then 100 then you have either a lot to do or you have forgot to enable some cache.
There is several old by still valid forum thread here somewhere about eZ Publish setup optimization that covers most of these things.