Meat has a specific heat of about 3.5kJ per kilo per degree, so say you weigh 70kg, that's about 4 million joules to lose before you die.

At 650 joules per second, you've got slightly over 10 minutes.

4,000,000/650/60=102.57 minutes

But that's for a resting body, a shivering one would lose only like 200j/s

Also, you forgot one important aspect, if you're getting bathed by the sun and spinning, you're constantly getting heated up.