I do, all the time, and was commenting on it today. As soon as I stand, I have to go back back to my chair. I have chronic anemia, neuropathy, kidney disease, tinnitis so these maybe be an issue, and assume they tested your hemoglobin, creatinine, hearing. It can also be from surgery, and had a RND also, with the neck vein, nerve and neck muscle removed, so maybe there is lack of blood flow to the brain or something unrelated, like pain medication, sitting to long, other illnesses, so I haven't found out the cause several years later. I hope you find answers.