dream scenes flashes in my mind?

Yup,sometimes there are some dream scenes ,which are the vivid ones ,flash in my minds suddenly.can someone explain why this happens?or can I do something with this in order to have a lucid dream?

When does this happen? As you are falling asleep, during the day or when you wake up? I’ve had fast images flash as I’m waking up, it’s reallys strange

I mean during the day.isnt it useful ?as it helps you remember a dream scene.

I sometimes get dream scenes pop up in my head too, I assume it’s my brain reminding me of little bits I had forgotten. Do you see flashes of a dream you’ve already had too, or is something completely different going on? In my case I do find it helpful, or at least positive since I know my SC is on my side and wants to remember.