I certainly experience that type of withdrawn, inward focused thought process/state of being where I feel startled and uncomfortable to hear my family or noises that pull me out of it. I believe that everyone stares off into space from time to time, but in my case, the way I react, so strongly, is partly the PTSD startle reflex, hyperarousal, where things seem more threatening than they are, and I get more irritable than a person without PTSD when I am disturbed.
As far as not sleeping well due to a head full of thoughts, well, many people have that- it can be anxiety (among other things perhaps) which ranges from occasional to constant, and on the other hand, sleep difficulties from a variety of causes are notorious in PTSD sufferers. I have sleep difficulties too and have dealt with thoughts that won't stop (anxiety) that kept me awake many times, though it's very rare lately where I am in my life now.