My van is overheating and I'm not getting any hot air in the van. Could it be the thermostat?

In regards to the overheating i still have plenty of fluid and everything else. I also have another problem with the van. When i start the van and sometimes when i am idleing the van seems to be a little jerky, like it is having a hard time staying on. It does fine when it's going down the road. I do not know it this is related but it is another problem i have with the van.