Sudden dizziness for a few seconds while sitting is caused by the following reasons: 1. The most likely disease for a patient with a sudden onset of dizziness that lasts for a few seconds and relieves itself is vestibular paroxysm. Vestibular paroxysm is caused by the compression of the vestibular nerve by blood vessels, which leads to demyelination changes of nerve fibers and thus triggers episodic vertigo. It is mainly manifested as transient and frequent episodes of episodic vertigo, which can occur several to hundreds of times a day and can be accompanied by tinnitus and hearing loss, and is more effective when given antiepileptic medication. In some severe cases, microvascular decompression can be performed when the effect of drugs is not good. 2. Besides vestibular paroxysm, there may be otoliths, which is the most common form of peripheral vertigo. Patients often show sudden attacks of dizziness, which last for a relatively short time, usually a few seconds or no more than 1 minute, and are related to changes of the head. For example, in patients with posterior hemimelia on the left side, dizziness can occur when the head is turned to the left. In patients with right posterior hallux valgus, dizziness can occur when the head is turned to the right, which is mainly treated clinically by manual repositioning; 3. There may also be vestibular migraine, which is mainly manifested by recurrent episodes of dizziness and vertigo, with or without migraine symptoms, lasting from a few seconds to several days, and patients often have a history of migraine or family history when they are young; 4. There are also some rare causes, such as transient ischemic attack, hypoglycemia, anemia, epilepsy, cardiac arrhythmia, etc. These need to be further examined and clarified in the hospital.