There are number of reasons related.
1. Acidity
2. Motion sickness
3. Medicine inducing vomiting
4. Food poisoning
5. Stomach infection
6.Early sign of pregnancy
Many many more.
Next Steps
Take online consultation option as inedd to check your history even.
Health Tips
Avoid junk food, have proper sleep, drink plenty of water,As per your history other life style modifications can be recommended