Detached and dissociated autonomous moments like that are very common for me. Maybe once or twice a week, rarely a couple times a day.
In my case I know it's drug abuse, from months on end of chemicals like PCP. But you've described it very well.
I'd say it's like viewing a recording in true 1st person with your own 5 senses.
It's worse than deja vu because it's both 'you' and 'not you now, but still you', so to speak. Even though you act normal as you would, not like some drunk or anything, it's still very, very unsettling.
After a particularly long moment when I finally regain some semblance of self control, all I can do is close my eyes and think 'holy soykaf', and wonder when it will stop. If it ever will.
Surely it has something to do with the NMDA receptors and can be treated through diet and natural repair. I don't really know.