Yes, I have an OBD II scanner and there are no codes presently. Please keep in mind, It starts right up when cold. The starting problem is only after it has been diven and sits for more than 5 minutes. It is driven 85-90% on highways and occassionaly get WOT accelleration. S/B no carbon. Battery is original but cranks engine with no problem. Fuel is always premium but often from inexpensive stations. About 6 months ago, I had codes P0345 & P0346 Camshaft Position Sensor A Bank 2. I replaced the sensor, cleared the codes and have no codes since. Could that be related?

 

I would still have battery tested, to be sure it good. What are Fuel trim values? What does coolant temp sensor read when it happens? Have you checked ground connections?

 

The battery has checked out good, this happens with the fuel at all different levels as well as the temp at normal or a lille less than normal levels.

 

I have similar problem with my '99 Seville STS. I suspected it's a fuel problem because depressing the gas pedal hard will cause the car to start quicker than trying to crank it over without depressing the gas pedal.

There is a strong smell of fuel quite often so I need to get it in and have all the fuel lines tested. I had a similar problem with another large GM saloon years ago, turned out it was aged fuel pipes, when engine was hot the pipes due to age provided little protection as a heat shield and therefore I got fuel evaporation/starvation. Full set of new fuel pipes to the injectors and problem was solved.