Usually, this is associated with a large notebook or the Mathematica front end is struggling with too many things going on.
Try resetting the initialization files (http://support.wolfram.com/kb/12464).
If that does not correct the problem, contact Technical Support (email@example.com). Tell them how you start Mathematica, the symptoms (example: how long does Mathematica stay in this state), and include your Activation Key or License Number. It would be useful to know if you can run the Mathematica Kernel (http://support.wolfram.com/kb/12414).
I emailed tech support. You are just much more responsive than they are. At stackexchange.com the suggestion was to remove wireless components so I installed the demo on my laptop that has a hard-wired monitor, keyboard, and touchpad, and running Widows 7, 64 bit. Mathematica 10 worked perfectly. No way to do this with my desktop.