I'd add in a motility disorder such as delayed or too fast stomach emptying, an esophageal disorder as well. I feel super shaky with nausea and bloating and mine is due to motility problems.
There are many causes of nausea, the most common are:
1- Anemia
2- Diabetes
3- Drugs and some kinds of vitamins
4- Gastroenteritis
5- Gastroesophageal reflux
6- Irritable bowel syndrome
7- Cholecystitis
8- Nervousness
9- Peptic ulcer disease
10- Pregnancy
You can start by doing some investigation including complete blood count and fasting and random blood sugar. If you are taking any drug routinely, you can think of stopping it for a while or look for an alternative.
Going to a physician is the best option to do for now.