My 2003 Cadillac CTS shuts down mid-drive without warning and will not restart for about an hour. It will then run just fine until the next time that it does this.

they have a recall on that year for the ignition switch

It could be that your vehicle is engaging the "safe mode" upon restarting. Auto Zone and Advance Auto will perform a complimentary diagnostic check which will most likely identify the issue. The trouble codes are stored and may be retrieved even when your car is running okay.

A bad crank sensor will shut the jeep off suddenly, while driving down the road, then restart later and it repeats over and over until you replace it.

Hi, i'm also having the same problem. i'm gonna try to do what you suggest and let you know. Thanks.

check your camshaft sensor and try cleaning your maf sensor too

how many miles are on your car ? will it start up after it shuts down or do you have to wait 20 or 30 min. had a problem like this with my own car it had 1600,000 miles on it. do you have any warning light on dash when this happen, if not, it's most likley it is the crank position sensor. it's about $60.00 at the dealership, not fun to put in. also could be a fuel pump problem, have a pressure test done on pump first before you buy a pump it is about $400.00 + $600.00 to put in. I haven't seen to many pump problems without a lot of other issue while driving. If warning light are on, have the computer scanned first.

good luck bro,
i have done many CTS's like this and all turned out be the sensor.

Sounds like a possible fuel filter. Bigger question - when was last tune up? With the different grades of fuel these days and with temps fluctuating a fuel filter would be my first thing to change.

Next time it shuts down, try the engine immediately but listen this time for the fuel pump to prime, you may have to open your door and listen toward the tank. If you don't hear the fuel pump, then that may be the culprit.

You may have a bad throttle body.

I had a similar problem the car would start fine then when driving it would just stop - if i waited long enough it would restart just fine and the same thing would happen. I replaced the crank sensor and the cars been running fine ever since. Even though the sensor ohmed good when cool???