In year 25XX humans have started to colonize other planets and ship humans off earth to live on them. It had been many years since the initial wave of scientists and engineers went and established strong footholds on the other planets and now more regular people were beginning to move off world.
To get to most other planets great spaceships had to transport hundreds of thousands of people at a time. To save on food and longevity of life all passengers are put into stasis pods that are meant to hold a persons body at the same condition as when it enters the pod.
Author’s note: I know this sounds exactly like the set up to the movie Passengers but the actual story is about the end of the trip where the pods are opened and some people find that their pods had been malfunctioning throughout the trip leaving them significantly changed.
Example: A 40 Father wakes up at the end of the trip and finds out that his pod had accidentally set to keep his age at 4 years old and he now has the body of a child younger than his own daughter.