1992 cad seville cranks fikne drive a about 5 miles cools at about 200 degrees F
Cut off the engine ,computer sat battery at 12.7v car won't start. Turns slow . Wait a couple of hour it cranks right up just by turning key why?

It's called high resistance. I'm sure you know this. Heat... is resistance. The first place to look is grounds. Try running an additional ground jumper just for testing when this happens. Right from the starter body to the chassis.
A DVOM is the greatest tool for getting educated in matters like this. Testing the positive and negative sides the same, leads to quick diagnosis.
Next is the starter windings. Most probable cause IMO.

. Remove and fully charge the battery. Most auto parts stores will test and charge batteries for free. Just because your meter registers 12.7v does not mean the battery meets the amperage requirements of your car.

. Clean battery terminals and cable connections--apply dielectric grease. Ensure the ground is in very good shape.

. Clean starter motor connections and apply dielectric grease.

. Replace starter motor, if the problem persists.

kitch428 makes an excellent point. Amps=Volts/Resistance. As resistance doubles, amperage is cut in half. Resistance is increased by corrosion, smaller cable size, poor cable material, and heat. Electric motors (e.g. starter motor armatures) will have greater impediance and generate less torque when they are hot.

Taking this a step further, focus on corrosion and cable size. Smaller cables and corrosion greatly reduce the effective cross-sectional area of grounds. Based on the formula Area of a Circle = Pi times R-squared, as the effective cross-sectional area of a cable gets cut in half, the resistance goes up four fold. This means that the amperage available to the starter motor would be 1/4 of what it would be otherwise. That's why all of these factors influence starter motor performance, especially when they are failing.