Hi, I'm a 33yo male.
I realize this post is relatively old but I thought I would share my experience for others in case they find it helpful.

TL:DR: I was diagnosed with Intestinal Methanogen Overgrowth (IMO) - Formerly known as Methane SIBO. And it seems to have caused a cluster of symptoms which include: internal shaking sensation, bloating, fullness, constipation, GERD-like symptoms, cold flashes and last but not least, anxiety/depression (It feels like they're cousins).

My first symptoms were feeling of strange fullness, in head, neck one morning followed by very elevated heart rate (~140-160bpm) after when I finally got up for the day. This lasted maybe 2-3min. I was terrified.

Fast forward two months, and this cardiac event has repeated itself almost every single night along with feelings of fullness/bloating. I ended up doing the following tests; EKG, heart ultrasound, leg ultrasound (to check for blood clots) holter monitor for 5 days, and once everything came back clear, turned my attention to the gut. Ended up doing an endocospy, stool tests, blood tests, and the main one, a SIBO breath test which finally detected a case of Intestinal Methanogen Overgrowth (IMO).

The treatment is relatively high dose of antibiotics; 14 days of Rifaximin and Neomycin which I am actively following as we speak.

Learnings:
1. Not knowing what is happening to my body caused me great anxiety
2. Bloating/Excess gas can cause anxiety and trigger the heart palpitations (Check Roemheld Syndrome and vagus nerve)
3. Anxiety has probably been the worst of all symptoms and it needed to be managed.
4. Gas can be controlled by watching your diet, FODMAP diet seemed to help. Gas X also was helpful in quickly relieving bloating.
5. Feeling soft internal tremors seem to be directly correlated to the gut for me. I feel them most overnight and in the morning as I wake up. Bowel movements or gas relief seem to greatly reduce this sensation
6. Hormones can play tricks on you when all this is going on. I legitimately thought of several occasions that I had spilled cold water on myself but it was just what seems to be a localized cold flash.
7. Nerves felt weird and odd, I think related to anxiety.
8. Depression and feelings of sadness prevailed on some days. I think this is related to pint 6, the hormones.

Lastly: My anxiety was bad as I had a lot of life changes happening. Lost my job, had to let go of my apartment, was planning to move countries. Many things hit at once. It’s entirely possible your IMO diagnosis (or any other) may not cause so much anxiety but for me it did. It felt like my life was completely on pause.