GNex cannot hold a signal.
So, I've come to notice this in the past couple weeks or so, when my Galaxy Nexus is in my pocket or on my desk or whatever with mobile data on, it'll turn off within a few minutes. And then when I unlock it, it'll usually turn back on or sometimes, never. Then to turn it back on, I need to disable mobile data, go into airplane mode and then turn that off and turn mobile data on again. It's a hassle and more than that, I'm missing all my Whatsapp messages. This is a serious inconvenience. I went to my network operator and got a brand new sim as I thought the old one might be causing issues.
Another side point is that even when I'm using the phone, it simply can't hold a strong signal like it used to. My neighbour's Note 2 on the same network has no issues. However, my phone displays a Edge signal when I'm suppose to get full bars of otherwise fast Internet.