I had to quit office work for this reason. Now I work in education and get to pace moderately or stand all day and its been a lot better for me energetically. Had that 'Big dog in a little apartment' feeling.

I'd suggest drinking Yerba Mate throughout the day. Maybe get a standing or walking desk?

I have this issue where I will get super antsy by the end of my shift and just HAVE to hop off my PC, I work from home, and literally the SECOND I walk away and am free.... I just crash and I'm laying on the floor in my office and loose all motivation. Like it's mentally exhausting and when I'm free my mind just wants to not think or do anything. Some days I just zone out and stair at the ceiling for a while. Or turn on a TV show I have seen a half dozen times just to have something mind jumping to act as background. My body will have energy, but my mind loses all drive to focus on anything. I think stress is a big factor but I have just been stuck in this rut. I recently started physical therapy for my back and hip that's been messed up for months now. I spend 2 hours a night there 2-3 nights a week and on off night I always plan to do some of the stretches at home but then I just... Don't.

Do you stretch? This helps me a little psychologically to calm me down. Realizing my muscles and tendons are shortening because Im sitting for hours gives me anxiety so I have to stretch the right muscles (largely hamstrings and hip flexors) to prevent that. Helps too that it will get your blood moving a bit especially if you are a bit more dynamic with the stretching.