I am glad to see this post OP.
I have been experiencing this for several months now.

I catch myself drifting into a different world, similar to this one, but with a more genteel, pleasant feel to it. I feel as if I have stepped back in time a bit as well, how I imagine it might have been 100 to 200 years ago.
I find it happening when I'm in a relaxed state, while driving is the most common and I enjoy the way it feels so much that I don't want to return fully to this reality.

Once I realized this was happening I began to ponder what it was and I am wondering if I am transitioning into another dimension as the vibrational energy is shifting on earth.
I am being drawn into a dimension that my vibration is a better match to and one day, POOF! that may become my "real reality" and this life will be a fading memory.