After recovery from suspend, shortly thereafter, system reboots without user interaction. A workaround is available if you're willing to sacrifice suspend-to-ram for suspend-to-idle. The BIOS has two "Sleep State" options, called "Windows" (suspend-to-idle) and "Linux" (suspend-to-ram), which you can find in at Config -> Power -> Sleep State. If you change the setting to "Windows", this will change the state from suspend-to-ram to suspend-to-idle. You can see this if you run cat /sys/power/mem_sleep before and after the change.