I don't expect a fast oxydation that set them in flames, but I expect them to fell what you would feel if you take a bath in bleach.
To get a nice fire instantly on Earth, you need something like the substances in https://en.wikipedia.org/wiki/Autoignition_temperature . The ones with low temperature are
Triethylborane −20 °C (−4 °F): It looks like something that you could find in Titan, but I don't remember reading about that. The structure is not so weird, and there are some similar molecules with nitrogen instead of boron. I don't remember massive natural production of organic molecules with boron, but boron chemistry is very weird and well above my chemistry level.
Silane 21 °C (70 °F): It would be more strange to have too many organic molecules with silicon.
Phosphorus (white) 34 °C (93 °F): I don't think it's stable enough to be acumulated naturay. It's too energetic and I expect it to react with some of the molecules in Titan.
What are some of the chemicals that would vaporize and oxidize instantly in Earth’s atmosphere which this hypothetical Titan life could be made of?