I just updated to Mountain Lion (10.8.2) from Snow Leopard (10.6.8) on a 2008 Macbook Pro. After updating everytime I close the lid to put it to sleep, upon re-opening the computer reboots. At first it seems to try and wake up but then just restarts. I have not enabled this in System Preferences -> Energy Saver (see screenshot). Can anyone suggest what might be happening? Currently it is making the computer fairly unusable as bootup takes quite some time on my machine. ML is definitely slower than SL at least for me.