I do not recognize the plant.
There are quite a few "old man" cacti (anything with white hair qualifies, apparently) ... usually columnar and upright (Cephalocereus, Oreocereus). This is something different from those. I would remove any stem that is narrow and no longer green (dead, or on its way out) and hope the happy green stem visible at the base will branch.
It is hard to tell if some of the different growth evident in the photo is due to low light conditions. The main stem (bottom half of first photo) has narrow and wide parts, and I suspect the difference there may relate to how much light the plant was receiving when it produced that stem. The narrower parts will tend to be weaker, even once the light has improved. Anyway, this is kind of a clue that you will benefit from providing strong light and looking at the width of new stems to confirm you are meeting the plant's needs.
