Just had thyroid checked. It's fine. I am post menopausal. 64. I had them this morning in lower pelvic area. Mild, about a 3 on scale of 1-10. I would give anything for a Dr to try and find out the cause. I researched diaphragmic flutters and got some answers. I even did the exercise to relax the diaphragm months ago and it works at times, the vibrations stopped for that moment. How are others with activity? I'm not very active since I retired but then I started with these in 2019 when I worked full time. I swear it's diaphragm related. Injured or irritated that nerve.