Sometimes when I have been sitting for a period of time and I get up and start walking, I start to get tingling and numbness in my hands and can feel weakness start to spread and I start to black out. I usually will grab onto something and try to stay conscious. The typical time this happens is when I have been sitting in my car in traffic for long periods of time, however, it has started happening during our Sunday service while I am sitting in the choir loft. We sit during the sermon and then stand up to sing an alter call hymn.
Welcome to Chat Doctor! After reading the query I can say form my clinical experience that the symptoms suggest that (most possibly) you have orthostatic hypotension- in which there is a sudden fall in blood pressure when one stands after sitting for some time. I will advise that you should get your blood pressure checked-in sitting and lying down position and see if there is fall of blood pressure ? Also, you might be having some high blood pressure which is not treated or treated partially and you need to revise the medicine. You should also get thyroid levels, sugar levels done, an ECG will also be helpful in ruling out other cardiac cause. You seem to be otherwise healthy person as nothing more is mentioned, so, the above causes are most possibly involved. I think by getting the test will pinpoint the diagnosis and solve the problem. Hope the reply is usefulness free to ask more questions