.....

I have had many of the same problem, only for me it happens when I go to hevily populated areas like spawn, so im guessing lag.

It has to be a plugin problem. Do you have another plugin that allows /spawn? The console won't crash but the game will. A frequent problem I run into. Try turning off some plugins, and doing the same things to reoccur the problem. If it doesn't crash, you know which plugin is messing it up

Nothing appears in the console when it crashes(Or a crash report), so I don't think that's the problem, its probably not enough RAM, which I just found out that a 32 bit Java can only allocate up to 1 GB.

That is a lag out error...aka not enough memory/ram to have the chunks generate. Can you paste your whole console via pastebin as well as a crash-report if existing also via pastebin. That way I can make sure it is not an out of control plugin.