Yes. When I first got it ($10 Ikea side table, similar to OP setup) it was hard to stand and concentrate on work for a few weeks. Now I barely notice it and much prefer to stand. Sitting makes me antsy.

I also started working out around that time. Had a hard time squatting 100 lbs. So no wonder it was hard to stand for the first weeks with the standing desk. I was in extremely bad shape.

If you have a lot of trouble standing you might be seriously out of shape too.