I have had random bouts of this from as far back as I can remember too. It is excruciating when it happens...To me it is kinda like a chaotic sped up audio track that I can't slow down, stop, or panicing while trying in vain to figure out how to save a cassette tape that is being eaten...overlapping visual like movie sometimes clear progression of story or sometimes like a,slideshow with paced images that are mixed up or completely random...The sped up audio is not just out of sync w/ the images...they usually do not have any obvious connection but there is always something familiar about it all??!! But can't quite remember why? But try to control and get them on the same speed track and is so frustrating because can never regulate it...and leaves understanding just outta reach.... as far as starting stopping it is like waking up on a amusement ride... I don't know how I got on the ride and it's just starting to move...so just gotta hang on and bear thru...when ever it is over It Just Comes to a stop and the bars release.... I do not know the cause,.. I have accepted it as part of DR/DP...but often wondered if it could be either neurological or sometimes think it may be sleep disorder related?? Idk.