This puts me in mind of Jack Chalker's Well World series:
The Well World series is a series of science fiction novels by Jack L.
Chalker. It involves a planet-sized supercomputer known as the Well of
Souls that builds our reality on top of an underlying one of greater
complexity but smaller size. The computer was built by a now-extinct
race, the Markovians, who developed the Well of Souls with the goal of
creating a new species that would transcend their own.
The Well World is the planet that houses the Well of Souls, and it
exists within the original Markovian reality. Its surface was used as
an experimental site where the Markovians tested their species designs
before sending the successful ones into the new universe to populate
planets. Humans are one of many such designed species who now live in
the "real" world. During the time period of the novels, the Well World
has been abandoned and left on its own for an unknown length of time.
The books mainly follow a mysterious character known as Nathan Brazil,
who has an (initially) unknown connection to the Well World. The books
are adventures that follow Brazil and a changing cast of secondary
characters through a series of visits to the Well World over a period
of hundreds (and millions) of years.
The All The Tropes Wikia page for Reset Button has this to say on the series:
Jack Chalker's Well World series has a universal (as in, resets the
entire universe) reset button in the vast computer known as the Well
of Souls. Only one problem: You have to destroy the entire existing
universe, effectively killing everyone in it in the process. No wonder
the sole remaining guardian tends to wipe his own memory and has to be
dragged kicking and screaming back to the Well World to do his job.