Spontaneous Wanbustion

Spontaneous combustion is a type of combustion which occurs without an external ignition source.

In humans

Main article: Spontaneous Human Combustion

The spontaneous combustion of people (i.e. death from a fire originating within the victim's body without a direct external cause) is a theorised explanation for a number of unexplained cases, some of which are well-documented and many of which are not. The more convincing cases share the following characteristics:

• The body is completely or almost completely incinerated, while nearby furniture that should normally have been damaged under such temperatures remains intact. Damage is limited to the victim's clothing, to the area of the floor or furniture on which they died, and to the ceiling above the corpse.
• The torso is the focus of the fire, and if remains are found these are of the extremities, such as the feet.
• There are no traces of fire accelerant, and the fire does not have an evident external cause.
• The victim is typically alone at the time of death, and is thought to have been alive when the fire started, despite showing little sign of having struggled.

Various theories have been put forward to explain these cases, though none have yet achieved consensus.

Thank you Wikipedia. 

Now that you know what spontaneous human combustion entails I can continue.

Whilst driving through New Mexico me and my companions (my companions and I?) may have witnessed a near-combustion-experience. 

I remember driving on I-40 somewhere around Santa Rosa. Gaslight Anthem was probably playing. The window was slightly cracked and I started to smell something. I didn't recognize what the scent was nor where it was coming from so I continued driving. Less than a minute Ry in the back casually shouts, 'Wan you're on fire!'. I turn to Wan and I look at a relatively large flame around his tri-cep. From his view he can't see the flame. We kinda started to laugh while it happened then my first reaction was to blow it out. Totally made it worse. The flame grew larger as I felt as if I had a cape on. With my free hand I just slapped it out with amazing reflexes which resulted in black soot engraved into my index and thumb. Along with a victim who will never forget this experience.

Neither of us smoke and there was no ignition to spark in the car. This was the highlight of the road trip for me. 

Aftermath footage available.

Believe it, or not.