Yes I get that. Both - the 'here mentally but not physically' feeling that I reckon is a cold, or bug or something, no other noticeable symptoms just 'not quite right';
AND that mental dislocation feeling - not a clue what that is but it's damned freaky. It's like my body is some kind of machine and I'm driving it, sitting in my head with my eyes being the windows of the cab. I can watch my hand reach for a cup of tea and it could be one of those fairground crane games, I'm controlling my arm with levers but it isn't really mine. Damned weird. It just passes and I have no idea what brings it on.
Sometimes, I reckon you have to just admit that you really don't know what's going on, shrug your shoulders and just get on best you can. Like moods, just something you go through from time to time. I try not to worry about it and just go with it until it works its way out... as I know it will eventually!