When try to buy app or song from iTunes app or app store on iPhone 5 it seems to start stops and goes back to baseline in second or two

When I try to buy any app or song from iTunes app or app store on iPhone 5 it seems to start the stops and goes back to baseline in a second or two.

It did it with my old iPhone 4 in last month or so, and it I hoped it would go once I updated to new iPhone 5. The problem has transferred to new phone too.

I can't sign in to iTunes account on iPhone. It takes the password then resets to baseline. No error message comes up. On the base computer (pc) it will allow me to sign up and buy songs, apps etc. I can then sync the phone and put them on it. It just won't let me buy direct from the .

As there are no error messages I am at a loss what to do. I have updated the payment details on my account, and my husband has an iPhone 4 and has no such problems. We share the same wifi. I have tried with 3G as well as wifi, with no luck.

I am pretty much out of ideas, and have tried searching forums but there is so much overlap between queries that I can't find a similar problem from someone else, but I am sure it exists!

Can anyone please help me?

Thanks in advance

Sarah