That sounds a little bit like Generalized Anxiety Disorder (but I am not diagnosing you here). Look it up. Usually, people who worry way too much that they lose sleep etc for rather small issues fall in that category. I am hoping you don’t have GAD.
Joke aside, The problem there is not that you have nothing to worry about, it is the state of oblivion you have for a short period of time which makes you less worried about somethng worrisome, and your subconcious tries to wake you up to reality and you become worried of not being worried.
Makes sense?
P.S. It is somewhat like someone takes inoxicant and stops worrying (for time being) but as soon as the effect wears off, person gets overwhelmed with anxiety.