According to the present symptoms (shaking, headache, fear that “body forgets to breathe” during sleep) you might be experiencing some type of anxiety disorder such as panic disorder. Nonetheless, all possible organic disorders with the same symptoms mus first be be excluded.

Having a geadache is a common symptom for many disorders, most commonly sinus infection, eye disorders etc. for people your age, in their middle 20's. Beside anxiety and hyperthyroidism, shaking can be also due to a neurological disorder.

You can request examination from a neurologist to exclude neurological reasons for the shaking. Further, the presence or absence of a real breathing problem can be confirmed with auscultation and functional breathing tests (spirometry and peak-flow-metric). You can consult your GP about these.

If everything tests OK, the remaining possibility is that you are experiencing anxiety disorder. Fear during sleep sounds like a panic attack. Panic disorder is treated with Selective serotonin reuptake inhibitors (SSRI) and psychotherapy. You can the consult a mental health doctor should you need to.