Unsettled

I am experiencing a sense of physical and temporal dislocation that I had not anticipated, and I am not really sure where it is coming from.

Physically, I feel out of things. I find myself unable to sleep, ravenously hungering yet rarely energetic, and mentally dimmed, as if I had lost my edge. Mentally, I am feeling restless, almost bored, unable to retain things in my mind, yet not really having interest in doing anything.

The only change I can associate this with the ending of one job and the beginning of another. In all fairness, it's been almost three years since I've come to my current job - almost 4% of my total life (assume an average lifespan of 80), and 12.5% of my working career to date.

I guess I had not anticipated this sort of physical reaction - a sort of unsettled despondency, if there is such a thing. Have I become such a creature of habit that a change of jobs is so unsettling to me?