I have Gastroparesis...It is not uncommon for me to be ill for days at a time, so much so that I even struggle to keep water down (but throwing up water is better than dry-heaving any day of the week, so I just slowly sip luke-warm water, because it doesn't hurt my stomach as much as cold water does). After suffering for years with this, I was diagnosed by my gastroenterologist when I was 25, after having an MRI, upper endoscopy and a gastric emptying study. This condition is most common in older patients and for those who have diabetes - well, I'm 30 and not diabetic. They found it odd that this is my situation because I am overweight - and if this was my problem, I should be slim...well, I've got more goin on under the hood plus suffering for years of this has put my body in 'survival mode' so I hold on to everything my body absorbs...like a camel. Anyway, I have found that eating oily foods is a guaranteed trigger, so much so that I can't eat even a small order of fries. If I'm careful about what I eat, I can usually avoid puking every day (some days are unavoidable) but I am allergic to all the medications I know of that 'help' this condition (Reglan and Domperidone which costs a fortune and is not available in the U.S.)...I kinda like living usually, so I go sans meds and I'm doing ok with managing my diet...usually...friggin sweet potato fries...CURSE YOU for being so delicious!!!
Try cutting out greasy foods (I know this is difficult, but a trick I learned is to wait to season my ground meat until after it is cooked...I drain the grease and then add water to rinse a majority of the grease away, then season the meat (this is not recommended for bacon, just use paper towels to remove all excess grease from your pieces)). I do just fine with buttered toast and baked goods with oil like cakes, biscuits, waffles (don't eat at the waffle hut...it's just not a good idea for your condition).
If you do find that it's not just with oil (because oil is a trigger for my condition, but it's not the only one) and that you're randomly getting sick but you feel fine other than the moments leading up to vomiting - and then you feel fine afterwards...talk to your doctor about Gastroparesis or Chron's disease. I recommend staying away from nuts; but other hard-to-digest food does it to me too, like raw carrots, raw celery, flavored liquids that go into coffee (syrups and flavored creamer), fruits and veggies with 'edible' skin like grapes and cherries...I still eat them, I just have to limit my intake, because I only want to taste them once.