Tab 2 10.1 keeps turning on
i've had the same issue occur with the same symptoms.  used to work fine and then randomly started re-cycling as you mentioned.  several forums indicate this to be a pervasive issue as a result of a recent update.  

i just chatted with samsung tech support and they recommended a factory reset.  it worked.  but i worry as to whether it will just eventually re-download the update the caused the issue in the first place...