Hold power button to get power off prompt then press and hold the power off/shutdown button.. Reboots into safe mode.... Tried it just now and its snap city! It disables 3rd party apps.
Many apps will still work some not, but if you can feel the difference then you know its a 3rd party app or widget messing with your program. I have currents disabled btw.
Apparently on reboot all is restored, so its a win win test of your system. I can definitely feel less lag as it was making my normally calm self angry. So now I hunt the app or apps slowing things down.
Suck it and see.
Sent from my Nexus 7