1997 Cadillac Deville Warm start takes 3-5 seconds of crank

Hi vernonite, Welcome to 2carpros and TY for the donation.

A good place to start is check and test the thermostat and coolant temperature sensor and clean out the idle air control valve-Get back with some results

Would the digital dash display of coolant temperature be using the same sensor? Thermostate was replaced about a year ago and appears to be working correctly as viewed by the dash coolant temperature values. Warms up to about 196 degress in about 5 minutes and then stays there. Starting problem only occurs after driving at least 5 miles and then parking about 15-20 minutes. A short stop like a minute or two does not cause the problem. What is a idle air control valve?

I've looked for a engine temperature sender gauge switch -none for yours-its picking up the engine temperature from the coolant temperature sensor-also be advised the thermostat controls the engine temperature, the CTS only reads it for other purposes

Start problems might want to check and test the fuel pump relay and fuel pump/oil pressure sending unit

IACV: Idle Air Control Valve-try cleaning it out and see what happens

Pull the vacuum line from the fuel pressure regulator and check the regulator for passing raw fuel into the intake system. The regulator is mounted to the rail, at the rear trans end.