I would begin with understanding the scope of my disconnects. is it all devices at the same moment? or just this single device. Currently, on my Macbook pro, I have an SSID my computer refuses to connect to automatically. When I look at the SSID properties, "Connect Automatically" isn't specified. Lacking this, you might try in the morning after, before connecting the device to your wifi again, I'd simply restart the computer, to see if that kicked off a re-join. if all other devices are reconnecting, i'd start with trying to determine if my computer had an issue ( bad or old drivers).
so, quite the checklist
I hope i understand the question and am giving good guidance. I hope it works out.