Let me contribute:
It does not depend on the kind of life you live. The feeling is inside you.
I travel around. I speak four languages. I have a $700 camera. And a good job, doing what I like and being paid for it.
I know the Alps, I have hiked and skied there. Nonetheless, the same feeling you describe is very frequent for me. I consider myself, and wonder "Who is this guy ? Is he really me ?".
There are days when I look at myself in the mirror, and I am surprised. I don't know what I am expecting, but surely it is not the guy with the ponytail and the untrimmed beard that looks back at me.
Maybe the real me still lives in Italy, in Milan to be precise. I am sure he reads my books and listens to my CDs. He probably married a nice Italian girl, from a good family: they are having two children next year.
Or could it be that the real me stayed behind, in Pittsburgh ? He tried to enter graduate studies at CMU, failed, and is now hacking somewhere in the Pennsylvania State University.
Or he staid in Paris, his French much improved, probably programming in SAP. He rarely visits the Louvre, only tourists do that. He lives with a bisexual guy named Ahmadou, and they have already visited Algeria, despite the danger.
Traveling fucks up your mind really well. I can think of all these potential baffos, each on of them product of reasonable choices, possibly happier ones. Nonetheless, the current me is the product of those choices, which I cannot ignore.
But the body knows that everything could be different: I, you, we could be eating real ciabatta in Venice right now, watching the pigeons and planning a trip to the Punta della Dogana (Ezra Pound's favourite spot there). We are not; I am typing this on a dry meseta in a subtropical climate, you are who knows where, probably somewhere in the US, or Canada, or some other place.
Maybe this feeling we get, that you expressed much more clearly than I did, means that it is time for a
change.