If you think its hardware try replacing your keyboard and mouse. The awaken command is usally a key press or mouse move from the I/O devices. Trying a different keyboard and mouse may resolve your issue. A stuck key or a malfunctioning mouse that randomly moves slightly ( even one pixl worth) would awaken the sytem.
Check your power managment settings. Check and see if you have you system to auto awaken, maybe under your BIOS for "Auto-ON".