Sometimes I get lost in flashbacks that seem to go on for hours too. They come in degrees for me... sometimes it can be just a visual or just a physical feeling or just a re-experiencing of one sense. But then other times they sweep me away and I am not me, instead little ones are just reliving it all over again on their own.
And then like you say, it switches or stops and I get up and dust myself off saying "Well that was weird" and then on carry on with my day in a shell-like way.
Sometimes I have them over and over in a day, and day after day.
Sometimes they come once a week or once a month.
I hope they ease for you Always changing. They can really zap you.