There are so many things that could cause us to "shift", as you put it. The body is basically designed to be symmetrical - the same on both sides (if everything's "correct", which is rarely is with our bodies). The skeleton is held in place by a complicated system of muscles and tendons and ligaments. So if, for example, you have a muscle tighten it can pull that area out of its correct alignment. If it occurs reguarly in the same spot, the muscles can literally shorten on one side and legnthen on the other, leading to regular misalisngment. Take the example of us women always carrying a heavy handbag on our left shoulder. Do that for years and you'll likely have a problem on one side of your neck. I have learned I can never carry a shoulder bag, and it took a year or more of regular stretching to get my neck muscles relatively straight. I say relatively because they're not ok due to cervical problems which are related to the bones in my neck. See, it's all so complex! Right now I'm wearing a belt to help tighten the ligaments in my SI joint (around the hip area) which my physical therapist told me loosened when I took a bad fall. Ever since then if I don't do exercises to tighten the ligaments, they loosen, the joint shifts and my body is out of line. Add to that it puts more pressure on that sciatic nerve and all my pain cranks up to an 8 or more, even with meds! So yes, we can shift! The sad thing is it's very easy to stretch a muscle, etc., and takes oh, so long to fix it, and in some cases, depending on what's causing it, it may be a condition you have to manage rather than cure.
Hope this helps.