I have never, never been a morning person. But near the end of April, I started walking up between 4 and 5 as well. I am planning on rearranging my sewing room this week and have fabric for two cushions for a chair in there to make it more comfortable for handsewing (and reading) when everyone else is still sleeping. A more mature friend has suggested that my body is going through the 'change' and maybe this is why it's happening. It still takes me about an hour to really wake up. 5:18 seems to be my most consistent time.