Insomnia a sleeping disorder in which an individual is unable to sleep, fall asleep, or stay asleep for the required period.
This is not a major sleeping disorder but it can become dangerous for your health if it turns out to be chronic. Although, sleep deprivation is not even for a shorter period because it causes another chronic disease like Diabetes, hypertension etc.

https://www.resmed.com/in/en/consumer/insomnia-symptoms-causes-consultation.html