Smart Phone "Jitters"...Why?

First of all, not relevant to my question, but I happened to see my T-Mobile Samsung Galaxy S4 that I bought brand spanking new in February of 2011 for $184 is currently on sale at Wallmart for 97 cents! Sigh.

At any rate, my new problem/question:
Lately my phone is sort of doing a little “jitter” dance while in my hand. I can be talking to someone and it does its little dance, or I can be reading a news story and it does its shaky vibrate. This doesn’t always happen, but at least once a day or every other day.

Yes, I always have my phone on vibrate instead of “ring”, so that is not the problem. Plus, this is a different vibration - I can only describe it as a couple of quick fast vibrations/jiggles as if holding an electric toothbrush for a second.

Is this some kind of reaction to automatic updates or something? Why is my smart phone shuddering (other than it knowing it is now on sale for 97 cents)?

Email, text , or low battery notification most likely. Or a pUsh notification from an app, like Words With Friends. Go into your settings and turn off notifications and see what happens.

^^^^ What Bob said.

Does it feel like the vibrator, only in a different pattern? Or does it feel like a completely different source? I think that device has haptic feedback, which could be felt like a vibration if you aren’t expecting it (or if it isn’t done properly).

Haptic feedback is often used for cap-touch buttons. Do you have “buttons” that don’t actually move, but kinda feel like they vibrate when you push them? For instance,I currently
carry a Motorola Photon. The Menu, Home, Back, and Search buttons work like this, while the side keys for volume control and camera are traditional switches.

As for seeing it on sale for almost nothing…a year is a really long time in cell phone technology!
-D/a