You can try to disable all wake up events for ACPI S3 in BIOS settings:
USB wake up from S3 [Disabled] (was enabled prior to this post)
Modem Ring Resume [Disabled]
PME Event wake up [Disabled]
HPET Support [Disabled] (High Precision Event Timer, was enabled prior to this post)
Power on by Mouse [Disabled]
Power on by Keyboard [Disabled]
AC Back Function [Disabled]
Power on by Alarm [Disabled]