A few days ago I wrote about getting up and going with your PinePhone. Included in the post were a couple quick fixes for things, like the WiFi. The fix in that post involved a reboot, but today I found one that works without rebooting your phone!
The issue is that the WiFi driver doesn't reload correctly when the SoC is put into suspend mode. I discovered on the postmarketOS WiKi page for the PinePhone that the fix is actually rather simple: just unload and reload the driver manually.
sudo rmmod 8723cs sudo modprobe 8723cs
The WiFi should the reconnect by itself. It's still rather annoying and the WiFi can die faily often, but this will at least keep you from having to reboot.