You might want to give iotop a run - it pretty much gives you a top like overview of all processes running and their IO usage.
This might help identify the ones that are high. I’m my experience one high IO from a single VM can affect your whole system. First thing I also always check is RAM and Swap usage - the second you have high SWAP IO will go through the roof - a reason not to enable Swap on SSDs.
how many processors does your VPS have allocated to it? a load of 4 can range from really bad on a single core system to 'meh' on a quad (or more) core.
also, when you're seeing the higher load, try using iotop to see if there's any specific process using a bunch of disk i/o that could be making other programs non-responsive.