This is a common question I get on a daily basis. In fact, there is no one thing that is causing this slowness, but a combination of several things. It could be an application that is taking all of the resources, such as SQL. (or what I like to call, Miss Piggy) You could have too many things open, like so many app windows on your phone, your computer will continue to run applications in the background or 'hidden from view'. Your anti-virus could be running a full scan while you are trying to work. OR Maybe, you have not performed some very needed maintenance on your system and it is crying for help. I have put together a video of some easy steps you can do to help speed up and clean your system.