1998 Other Saturn Models Starter fails when car is warm

I have a 1998 Saturn SR2. It will start fine as long as the car has been sitting for at least 3 hours. If I drive it for more than 5 minutes and then try to restart it all I get is a "click" from the starter.

Luckily it's a standard so I've taken to starting it with a push.
Otherwise the car runs very well.

Any help will be very much appreciated.

Thanks