Hi! It's possible one of the drivers isn't working out during suspend. You can play driver whack-a-mole with 'drvctl -d <device name>' and suspending until it stops rebooting to figure out which one it is.
I recommend testing out hdafg and iwn first. sysctl ddb.onpanic=1 or core dumps (if savecore manages to put anything in /var/crash) may provide more info. Good luck.
