My iPhone vibrates when it's off?

Now I have felt a random vibration a couple of times while I have just been lying on my bed. I normally have my iPhone on my bed in case I get a text, but one day while I was on my laptop, I felt a random vibration under my pillow a couple of times. I checked my iPhone, but it was actually turned off. But when I turned it on I had a notification so that was weird. Then today while I was lying on my stomach I felt another vibration underneath me, and checked my iPhone again, same thing happened. It was turned off but when I turned it on I had the same notification. So if this isn't my iPhone vibrating I have no idea what else it could be.

It was probably notifying you that you need to recharge.

Your iphone auto uptated to ios 8.1 and now it has a mind of its own… Its pretty cool heres a link o all it can do with ios 8.1…
http://www.apple.com/...pple=TROLO