intermittant fault with gear box auto?

Hi I have a Peugeot 107 06 reg. It is automatic and driving me mad. Every now and then I start the car and it gives a few shudders (a sound I dread) once this starts I know it will not go into any other gear but neutral however if i switch it off it wont go back on at all even though its shown as in neutral. Most of the time it starts perfectly well no trouble. I get no warning it can happen one day then not for another two weeks or more then it can happen three days on trop. has been in garage reset comp cost 100 every time but same things happen after a few days or weeks. Is anyone else having the same problem?? and what did they do? once it happens I have to leave it for a few hours then go back and it starts straight away.