Right now there is a lot possible starting point of world war III.
1..Japan and China >sinkaku islands, rich in oil and gas.
Possible, but not likely.
The costs are to high compared to the possible effect of such actions.
2. China & Taiwan and Philippines> panatag shoal and spartly islands both rich in oil and gas, Us will be drag because of mutual defense treaty.
Meh
China has more to gain from stability in the region, even though they may show some strength and be disruptive.
3.NorthKorea, its brewing. In times of war 90 percent possibility china will help north korea.
Meh.
NK might do something stupid. (Which is not helped by US's confronting line -NK is like an attention seeking child and US plays along instead of being the sensible one at the sideline.)
But I doubt China will step in except as negotiators.
I think China sees NK as a loose cannon and not like something worth defending too much.
4. If Israel attacks Iran. US and Russia possible china will be drag to war because its one of their biggest oil supplier.
Meh.
Doubt Israel will do any first attack, they have enough problems as it is, and Iran knows that US will step in if they attack.
If there were to become a conflict, russia might support with equipment, but they will get a deal to get their oil anyways.
Don't think US would risk being tangled up in another war if they can avoid it.
5. Syria. If Israel attacks Syria. Russia and US will be drag to war.
Meh.
Israel has nothing to win by this, and Syria does not have a proper rule ATM.
Would not be too surprised if there were some border-attacks by Syrian warlords though. But not something that is likely to escalate.
Remember that China own a huge amount of US debt. If they wanted to hurt the US, they would simply sell their debt and collapse the dollar. They could also stop export to US. This would hurt both nations. But China could still export to europe knowing that a lot of the export would be resold to the US, but then at a higher price which would hurt US more.
I think the current world power balance are pretty stable, too stable for something like WWIII, things going on in south china sea would be nothing bigger than a conflict at the worst. and most likely it would never happen. And China would never risk everything to support NK b/c that's against it's best interest