Often what can trigger this to surface is when a person is being challenged in the now where they feel powerless and under a lot of stress.

A question that is constantly asked of a victim is "why did you wait so long". With all the AWARENESS of abuse coming to light now, it's not surprising that some victims are dealing with things they endured what could have been years ago. The mind tend to shut down when experiencing a rape for self preservation and this can leave someone with unresolved trauma that begins to resurface like what you are describing. Trauma is stored in a different area of the brain where it can be dormant for years until something in the now can bring it forward.

It's very important that when you experience these flashbacks and yes they can happen during the night, that you acknowledged that did happen but not now and that you are "safe" now. It's not your fault this is happening either, you did not do anything wrong.

It may help you to get therapy doing EMDR which helps a person to process traumas that they did not have enough life experience to process when the trauma occurred.