Sleep inertia is a transitional state of lowered arousal occurring immediately after awakening from sleep and producing a temporary decrement in subsequent performance. (1)
There is study demonstrating what increases sleep inertia
One of the most critical factors is the sleep stage prior to awakening. Abrupt awakening during a slow wave sleep (SWS) episode produces more sleep inertia than awakening in stage 1 or 2, REM sleep being intermediate. Therefore, prior sleep deprivation usually enhances sleep inertia since it increases SWS. (1)
I am interested in what can be done to alleviate sleep inertia (rather than reducing the causation).
Finally, sleep disorders represent risk factors which deserve new insight in treatment strategies to counteract the adverse effects of sleep inertia. (1)
(1) Sleep inertia.
Tassi P, Muzet A.