I just read your reply to another post in which you mention being over weight. That and any low blood pressure and/or heart rate would cause a dizzy spell when changing physical activity level, such as standing up from a couch, especially if one has been sitting for a long period (more than 10 minutes is my metric). This can happen to me just from sitting in a doctor's office waiting for a call to come in. Not that I go to the the doctor all that often, but I can say when I do (dentist, eye, primary, cardiologist) I take my time getting up to prevent a "public" dizzy spell. I am less careful at home as I can just grab a chair or the wall and stand still for a minute, that's about all it takes.
If you normally don't have any dizziness from a rapid change in physical activity, I'd think about discussing it with a doctor. My problem is AFib driven and the inability of my heart to efficiently respond to a change in need for more oxygen. Once I start moving I can go for a mile or two (not up hill please) without any further dizziness.
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