1985 Chrysler 5th ave shuts down HELP

hi. I have an 1985 Chrysler 5th ave with 66000 miles (but may not be acurate). I can get it to start most times. But when the temperature reaches normal, the whole cars loses power and the engine shuts down completely and I cannot get it to restart untill it has cooled down (somtimes hours) I am buying a repair book but I dont know where to begin. Where should I look? What could cause the car to lose power / engine shut off when the temperature reaches normal or anything above cold actually.
Please Help ASAP
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