I've been unable to consistently reproduce this occurrence, but my guess is that because of my character wearing full Ghillie Suit and Leather Clothes that my Heat Comfort Value is so high in Sunlight that the game thinks I am standing in fire.

My Character: http://puu.sh/tH2fw/fcecbce512.jpg

UPDATE: It appears this only occurs when just logged into a server and wearing a ghillie suit. Taking off the Ghillie Suit and putting it back on solves the issues and no more fire damage is taken. This also seems to only occur while sprinting in daylight.

After some more testing I can confirm that this seems to be related to wearing the Ghillie suit with leather clothing in daylight. Been taking off the Ghillie suit, holding it in the hands, while running around more without taking fire damage.