Intermittent fault with getting itunes to recognise phone

I have an intermittent fault with iPhone 4s - when I try to connect to ITunes I sometimes get the message 'iTunes could not connect to this phone - an unknown error occurred (0XE8000084)'

I have updated all drivers, uninstalled iTunes - reinstalled etc. My old iPhone 3 and IPad connect OK so am thinking it is the phone at fault.

I have tried the cables but still the same - after many attempts and jiggling around it will sometimes connect.

also get the message 'windows does not recognise this device' and to reinstall drivers - but I have - no difference.

can anyone help please before I end up having to have an expensive repair

Thanks