hormonal anxiety
There was a period where I’d wake up in the middle of night feeling very scared over nothing at all, with a racing heart and just a horrible gut feeling that something awful was going to happen. I spent so much time online looking for reasons why this was happening - completely confused by all the information out there - and eventually began reading about what hormonal changes can do during your late 30s and into your 40s, as they often cause nighttime anxiety and problems sleeping.
What helped me the most was finding a program that put everything in simple terms and told me exactly what to do. Once I understood what was happening to me, the intensity of my fear went down tremendously.