What is your blood pressure? If your blood pressure is too low it's probably due to the very low level of sodium in the Paleo Diet, which is usually a good thing for most people. For some people, myself included, you need a higher level of salt in your diet to keep your blood volume high enough to get blood where it needs to be (like your brain for instance!). If low BP happens to be the case, then try adding more salt to your diet in the form of unrefined sea salt, but never table salt. Also make sure you stay hydrated by drinking plenty of water.
Alternatively, it could be caused by hypoglycemia (low blood sugar). How long ago did you adopt this way of eating? It could be that your body has yet to adapt to burning fat as your main source of fuel. Also, what do your macro nutrient intakes look like, how much protein, fat, and carbs? How many calories are you eating each day? Are you sleeping well? It could be a lot of things.
There are dreams we’re taught are normal, whether it’s money or success or any of those things, but we shouldn’t believe in those things if they are not important to us. There is an ocean between our real lives and what is expected of us.” -Tim Lambesis