I have an issue currently where if I suspend my laptop connected to my bluetooth headphones, when I resume the volume will jump to max volume everytime.
However, if I leave the laptop on and turn off and reconnect the headphones, it will remember the last volume.
I installed arch using the archinstaller and am running pipewire and wireplumber.
Are you using Bluetooth hardware volume by any chance? Pipewire uses it by default I believe. Your Bluetooth headphones might just be resetting its volume everytime it disconnects and reconnects. You may want to look into using software volume control for your Bluetooth devices.