What if "I" woke up in someone else's body? I'm sure there are movies with this premise, where "someone" wakes up in someone else's body, but they have the memories from their previous body.

But if memories are just physically encoded in the brain, I don't think this scenario makes sense even as a thought experiment.

When "I" wake up in the other person's body, I would have all their memories and none of my previous memories. So I wouldn't even know.