iphone 8 stuck on loading cycle

Out of nowhere my phone started (I thought) shutting down, but has now been on the loading cycle (spinning circle) for hours. Multiple online sources suggest pressing the up volume, then down volume then the side button. The apple logo is supposed to appear in 10-15 seconds, but even when I hold the side button for 60+ seconds nothing happens and the spinning circle is still there. Does anyone have any other ideas? Thanks!