Saab: SAAB 9-5 Aero wont start after engine has been running and warmed up., saab 9 5 aero, engine indication

Question
Our 7 year old SAAB 9-5 Aero estate which has always been reliable in the 3+ years we've owned it has developed a problem. (It has high mileage, over 100k.)

Engine starts from cold no problem but after driving for 10 minutes or so, the engine gives a "cough" and then we know that it has reached the point where if we stop the engine it won't restart until completely cool again (which can be anything from 45 minutes to 1.5 hours!). the engine turns over, but just won't actually get going, so don't think there is battery problems. Is it some kind of engine temperature sensor that isn't working?

Answer
Wendy:
 As noted in my profile, my direct hands-on experience is limited to the older 900's. However, I can say in general terms it is likely a temp sensor...or faulty connection (corrosion,etc) to one. Is there a "check engine" indication?
 If you have an AUTOZONE parts store near you, you can get a free error code diagnosis by asking..a good first step.
 Also, you may have a vacuum leak somewhere..it could cause similar conditions.
 Hope this helps,
             Jerry