To stop all currently running timers, you can simply use:
systemctl stop '*.timer'
To restart the timers later, you’ll have to remember which ones were running at the time.
timers=$(systemctl list-units --type=timer --state=active --no-legend | awk '{print $1}')
systemctl stop $timers
# ...
systemctl start $timers
(Apparently patterns for units don’t match inactive units, so `systemctl start '*.timer'` doesn’t work.)