Wifi Grayed Out

I have an iPhone 4s 16gb.

The setting to turn on wifi is grayed out.

It had this problem and I re-started the phone a few times.

Wifi would work temporarily and then not show up.

I upgraded the phone to 6.1.2.

Before upgrading, I backed the phone up on my Macbook Pro.

I am still unable to turn on wifi.

Any suggestions?