Can you envision another world war ever occurring?
If so, how do you think it would start? And maybe what kind?
I think it's possible. I do think that most countries would be reluctant to engage in a conflict of that size, primarily because they have a lot to lose, but I think it's still possible. I don't think it'd be WW2-like, with countries seeking domination. I think it'd be more WW1-like, where a series of smaller events ends up setting in motion a bunch of falling dominoes and triggers a larger conflict.
Potential scenario: US and China do a "face down" in the South China Sea. Some incident happens, a ship gets sunk. The other side feels the need to retaliate, and it just snowballs from there, dragging other surrounding countries in who now feel the need to protect their interests. This then invokes self-defense treaties, other countries reacting out of fear and/or self-protection, and so on.
Note: I an not saying the it will be us and China and/or over the South China Sea, just throwing that out as a possible type of example.
I am not sure about nuclear weapons, but if they are used I believe they would first be used by a country that is on the verge of losing as a last ditch desperation attempt.