I prefer test, then change bad parts personally.

Check the charge on the battery if it's in question. I'd load test it if you think the battery is in question.
Confirm the radiator is full, if it's not when you pull the cap, pull the spark plugs. Any fluid in the cylinders? I'd start by checking the coolant o-rings from the charger to LIM. Right the yellow ones.

If neither of those are the cause, try pulling the plugs and turning it by hand. Should be relateively easy.