Beginning with pipewire 1.2.0 some systems experience a lack of any audio output upon reboot.
In most cases this can be remedied by muting and unmuting the sound system.
In others it may be required to restart pipewire and/or wireplumber services.
This is generally considered a minor issue in the cases it does manifest, but there is a reliable workaround in relation to certain display managers.
(Tested only on SDDM, though it should be similar for GDM)
sudo machinectl shell sddm@ /bin/sh
systemctl --user stop pipewire.service pipewire.socket wireplumber.service wireplumber.socket
systemctl --user disable pipewire.service pipewire.socket wireplumber.service wireplumber.socket
systemctl --user mask pipewire.service pipewire.socket wireplumber.service wireplumber.socket
exit
This will stop, disable, and mask pipewire and wireplumber for the sddm user.
For further information please see the links below.
Depending on your system some of these may not be present but are included for completeness.
Upon reboot your sound should work again without any extra steps. 
References:
