Originally Posted by Mr. Ed
It did it again!!!!
It's switching available networks. Everywhere doesn't have 3G, so there you'll likely see E (edge), which is 2G. G is a step under that, I think it stands for GPRS. There could be random times where you'll see it momentarily switch to and from these networks, which are likely random incidences of being connected to different towers (e.g., you may not be able to connect to 4G while in a basement, so it'll switch to 3G). Traveling though, you'll see the type of network available in that area.