Those should be running periodically as scheduled by systemd.
There is no reason they should run on every boot unless they were not able to run for a long time, such as if you turn your machine off each night.
systemctl list-timers --all
to see a list of all these things, and you will notice that quite a few of them are scheduled to run at midnight. If you go days before letting the machine run at that time, and/or you did a lot of updates in the interval, both updatedb and man.db will have a lot of work to to.
for how you might reschedule these to occur when you are out to lunch or something.