People can say, even scream between sleeps due to some disorders, drugs or stressful conditions.
Talking while sleeping is harmless, can appear without a clear cause.
However, sometimes this phenomenon can occur due to some sleep disorders such as REM sleep behavior disorder or horrible sleep syndrome. Although different, these two disorders can make you scream or speak between sleep and suddenly become violent.
Some medicines, stress and fever are also likely to cause this condition.
Experts are not really sure whether the speaker follows the dream or even if this is related to the dream, but it can certainly happen at different stages of the sleep cycle.
Talking behavior sometimes appears when you sleepwalk . So for outsiders, you may look like you are still aware of your actions.