Memories don't usually just pop up for no reason. Pick a catalyst: A minor head injury or a fever dream.
"Why is there no plumbing?" or "Wait, is that magic?" 1 : I Recalled the Memories of My Past Life...
"This world is exactly like the video game I played before I died." Memories don't usually just pop up for no reason
Seeing an object that looks exactly like something from Earth (a toy, a book, or a specific tool). 1 : I Recalled the Memories of My Past Life...
Catching their reflection and realizing their face doesn't match the "soul" they feel inside. 2. The Mental Sensory Overload
"I remember why I died... and the person who killed me is in this room."