Random waves of unexplained nausea can have a wide variety of causes. If experienced short term, it is generally not a cause for concern. Ongoing random waves of nausea, however, should prompt a medical examination.
Unexplained waves of nausea can indicate infection of the gastrointestinal tract or other area. Infections may be bacterial (like food poisoning) or viral (like hepatitis).
Both over-the-counter and prescription drugs commonly cause nausea as a side effect. If you've recently started a new regimen, it may be the source, states the American College of Gastroenterology (ACG).
Nausea is one of the first signs of pregnancy. Known as morning sickness (though it can occur at any time), it can start two weeks into pregnancy and last through the first trimester, or in some instances the whole pregnancy, per the Mayo Clinic.
Drinking too much alcohol can cause significant nausea either the night you've been drinking or the next day. The ethanol in alcohol causes dehydration and can irritate your stomach lining, causing the nausea and upset stomach, according to BBC Health.
Mood disorders can manifest physically as waves of nausea. Conditions such as stress, anxiety and depression are often a cause, per the ACG.