The clinical term for the disconnect you're describing is called dissociation. At its mildest, dissociation manifests as daydreams. At the most severe, you're losing time. It's often a way our bodies cope with immense distress (think: learned helplessness and the freeze response). When the stress doesn't stop and the body can't seem to escape it, the best option is to check out and conserve energy.
To add some perspective: I chronically dissociate and meet criteria for Depersonalization/Derealization Disorder. My body feels like its not mine. For as long as I can remember, I've never been able to understand that the face in the mirror as my own. Usually I'm checked out of reality just enough that my memory feels the same as dreams. This due to my childhood was one where I was chronically distressed. My body learned to check out as a way to protect itself.
Feeling suicidal is often a response to distress. It makes total sense that your body decides to disconnect as a way to help stay regulated.