@tacitsentinel, There is an older discussion on Dysautonomia that you may want to view and read the posts to see if something sounds similar.

-- Dysautonomia/Syncope: https://connect.mayoclinic.org/discussion/dysautonomiasyncope/

You mentioned in the other discussion you started that you had a work related spinal cord injury. Here is some information I found that may be helpful.

-- "Autonomic dysreflexia (AD) is a serious cardiovascular disorder in patients with spinal cord injury (SCI). The primary underlying cause of AD is loss of supraspinal control over sympathetic preganglionic neurons (SPNs) caudal to the injury, which renders the SPNs hyper-responsive to stimulation." -- Autonomic dysreflexia: a cardiovascular disorder following spinal cord injury: https://www.nrronline.org/article.asp?issn=1673-5374;year=2017;volume=12;issue=9;spage=1390;epage=1400;aulast=Sharif
-- Autonomic Dysreflexia in Spinal Cord Injury: https://emedicine.medscape.com/article/322809-overview
-- Autonomic consequences of spinal cord injury: https://pubmed.ncbi.nlm.nih.gov/25428850/