Exact same with me. I can walk to an elevator but then not be able to stand to wait for the elevator to arrive. I can walk to my doctors appointments but I cannot stop at the reception desk to check in without needing to sit down. During crashes, it is worse and without much walking before standing, like just going into the kitchen and standing at the counter.
I have been able to check my blood pressure a couple of times during these events and it was very low (~60/50), but since changing BP meds I am no longer seeing these low readings during these events. (I never had high blood pressure before Covid, and when I briefly went off the medication I had fewer, if any, of these standing-lightheadedness episodes.
Interestingly, one of these episodes happened when I went to my first electrophysiology appointments for possible POTS (I was not diagnosed with POTS). So during the multiple standing/sitting BP readings for POTS testing, I was having very low BP when sitting (because it was immediately after my standing-lightheadedness episode at the check in desk). As my lightheadedness was recovering, my BP was going up, so during the POTS test it showed my BP increasing while I was standing. The nurse said, “This is crazy!”
Ultimately, I have never received any medical explanation for this standing-lightheadedness, nor has there ever been much of any concern from all my many medical providers. I am grateful to hear that others are having this exact same experience and that it’s not just me - maybe it will one day get some traction in the medical field.
Another thing: I had occasional bouts of this and other Long Covid symptoms prior to Covid. Very mild and only lasting a day or two, a couple of times a year. This started happening approximately after a bad case of the flu in February 2011. So, I believe this supports some sort of post-viral condition and/or a reactivation of something dormant.