According to the BBC,
Titan has rain, rivers, mud, and subsurface liquid. Of course, at Titanian temperatures of approximately -180C, the liquid is methane, and water is a solid rock tthrough which the methane rivers carve valleys.
Titan appears to have a lot of environments that may be analogues of those on Earth.
Could there be life sort-of-as-we-know-it in these environments–liquid-based life with some chemical reaction to live off? And maybe something like muscles or bones or stems? How much energy is available for life on Titan?
Odds are, there’s nothing like life on Titan. Unless there’s a heat source which brings local temps up to the point where water is liquid, it would be almost impossible for life to form.
Squishy methane clathrates might have some interesting potentiality, toss in a final electron acceptor like elemental sulfur and you might be in business. You don’t need a lot of energy for life, you need some sort of energy gradiant that life can exploit. The short answer of course is “no one knows.”
No one really knows what the source is. It could be volcanism, or it could be something else entirely. Don’t forget that on several planetary missions we’ve discoverd processes far different than we ever imagined, and based on that, I’d WAG that we’ll discover a process at work that has yet to be predicted.