Sleep Inertia is the transitional state that occurs between sleep and wake which is marked by impaired performance, reduced vigilance, and a desire to return to sleep.
Sleep Inertia's duration as well as intensity varies based on situational factors, but sleep inertia's effects may last from as little as a few minutes to several hours.
The term sleep inertia also describes the groggy feeling when you wake up in the morning after sleeping.
Hicham's syndrome is also another term and name for Sleep Inertia which is a physiological state of impaired cognitive and sensory motor performance that occurs immediately after waking up.
Sleep Inertia is not dangerous and goes away after awhile when you have had time to wake up.
Everyone experiences sleep inertia when they wake up even though they may not realize it.