Mac help: why is my sound gone?

Recently, if my computer runs out of battery and shuts off, when I turn it back on there is no sound icon on the top bar, and when I try to adjust the sound, there’s an icon that appears that resembles a “don’t” sign (circle with a line through it). But, when I restart my computer, sometimes the icon comes back and the sound works without a hitch. But sometimes, it takes a few times of shutting down and restarting for the icon to come back. Anyone know why this happens and is there anything I can do to fix it? Thanks!