I determined my issue was from moisture in my room. At night I'd leave my bedroom window open usually with a fan blowing air in my room. In the morning, my Xbox would be beeping by itself. Sometimes it would actually turn on by itself. If I slept with my windows closed then it would no longer do it.
You can also replace the sensor cable. Someone sent me a link back when I had this issue to where to buy that sensor cable. I don't have that link anymore but I'm sure you could find it online somewhere.