It is hard to know if this an effect of taking away some of the drug, increasing an existing behaviour or not. I pace when I am very ill and in a mixed state of bipolar. It becomes almost painful because I cannot stop. It can be anxiety, or agitation - which is not the same thing. I think it can be for me, my body trying to get away from my feelings and block out the pain/thought/destructive actions. A deep distraction to avoid something.
Sorry I can't be more help.