IPhone wifi button won't slide across?

My iPhone 4S wifi button won't slide across to turn on every now and then, as in its greyed out and when I'm lucky enough to be able to get it to turn on after numerous resets on my phone, it won't find any wifi networks.
However on the rare occasion it actually will connect and work but only for a few minutes before going off again. My wireless router is fairly new and my phone is up to date with software. My wifi is also very good on other members of the family's devices.

Any ideas!

Thanks:)

Turn it fully off then back on?

Take it back to shop and stamp your feet!

My boyfriend had the same problem nothing he did worked… Thhe guys at the apple store suggested turning it off and on again, and to back up and restore it and if that does not work to then go to the apple store if you have insurance on it still they can replace it for free

Back up your phone! Then do a full restore on the phone, After the restore if the WIFI still doe's not work then take it back to the apple store and i am pretty sure they will help you out whether you actually got it from the apple store or not don't really matter.