SharePoint 2013 Slow Loading Pages
This is a pretty common complaint, and frankly, one that is not entirely related to the product performance itself. The first thing that you should do if you run into performance problems with page rendering is verify that you are meeting the minimal requirements for 2013 to operate within normal parameters. The biggest requirements you want to ensure that you meet are the memory ones, which are:
Farm Server-12GB RAM
Single Server-24GB RAM
You can find more information on these here:
Something else to consider is FAST being the default search product now, that thing is a CPU hog! If you want to see how much that is eating up, start the task manager and search for the NodeRunner.exe process. You will see a shit ton of resources being eaten up by that beast. That being said, if you are meeting the requirements and the rendering is still slow, if you aren’t using search consider stopping SharePoint Search Host Controller and SharePoint Server Search 15. If you don’t want to actively turn off these, you should consider writing a bat file or something that starts/stops the search service in order to free up memory resources.