Why does my iPhone 5c vibrate randomly?

I recently got an iPhone 5c and IIm having some odd vibration issues with it. It's vibrating randomly.

Whenever it does this, I check my email and there are no new messages. I go into notifications and there's nothing there for that time-frame. In fact, the last time it happened, the most recent notification had been a full hour beforehand.

It happens whether it's plugged into a power adapter or not. It doesn't happen incredibly often, but does happen a few times a day.

I d just like to figure out what's going on with it.

People are not receiving my text messages?

I have an Iphone 5c with AT&T. I'm sending text messages to people who do not have me in their contact list (for my friend who doesn't have access to a cell phone at the moment). When I send messages to these people, they do not reply or see my messages. For the iphone users I'm sending messages to it doesn't say 'delivered'.
When I send texts to people who are in my contact list, and I'm in theirs, they receive my messages.

Do I have to be in someone's contact list in order for them to see my text message?

My iPhone 3G doesn't support my Apple Orriginal HDMI Cable?

I just bought an Accessory from apple and it seems its not supported. I used "Supported4" from thebigboss (cydia tweak) and its not working. I thought that it will fix the bug. Is there any tweak that i can use to fix this bug/problem?

How long will the iPhone alarm ring for?

My roommate left her iPhone in her room and locked the door.
The alarm has started going off on FULL blast and it's now been ringing for over 30 minutes.
I can't get in to stop it and she won't be home till tomorrow.

How long will this iPhone alarm keep ringing for? I'm seriously about to snap! LOL!

How long does your iphone last?

I have a Iphone 5s and depending on the certain apps I use, It will usually last me 3/4th's of my day.

Also for those of you who enabled battery percentages, how fast does each percent go by? To me it seems like if I'm gaming, every 3-5 minutes a percent goes down, and if I'm on messenger or something similar to that, it goes down every 5-10 minutes.