After stress and trauma, when the fight or flight response quiets down,
there can be a sense of being worn out.
These are just a few of the "symptoms" that seem to occur prior to, during, or after post-traumatic stress sets in for some people. It's also possible that only a few of these things are present. Although there are many things that can be the same from person to person, it is still a very personal journey. Remember these alone do not mean that someone has PTSD.
Medical teams have specific criteria that must be observed before a diagnosis is determined. Don't forget that one of the defining factors with PTSD is the re-experiencing of a traumatic event. Re-experiencing of an event is not always clear cut and it does not occur at the same point in the process for every person. Some can develop re-experiencing early on, but for someone like me, it took a year before the re-experiencing phenomenon kicked in.
This list certainly helps develop an appreciation for understanding why it can be difficult to diagnose PTSD and why it can take quite a bit of time before a determination is made. Remember also that not everyone who experiences trauma develops PTSD.