Hallucinations which occur at the 'start' of sleep is :
Hypnagogic hallucinations

These occur while “going” to sleep. Jactatio capitis nocturna, or rhythmic movement disorder is a neurological disorder characterized by involuntary movements, usually of head and neck, before and during the sleep.
Hypnagogic hallucinations
Hypnopompic hallucinations
Jactatio nocturna capitis
Non - specific hallucination