Problme with ’76 Buick shelf

HI US Car Fans, Maybe someone can help me here?! Have the following problem with my ’76 shelf 5,7 V8; every time I drive around with him and he is really warm, he goes out and jumps back on when he has cooled down a little. What could it be? I have already tried various things, but before I tell you what I have done I want to see what you say about it. PLEASE PLEASE help!!!! MfG Dine & Matze