From a very young age, I had extremely vivid dreams. The most vivid I can recall was a nightmare I had when I was living on Oahu as a child where my family was chasing me around our house, trying to kill me. My mom woke me up that night, telling me it was just a nightmare, but man it was vivid. Fast forward a lllooonnnngggg time.... I went years with only occassionally remembering my dreams, but more recently since my creativity took a spike in a good way, my dreams have been extremely interesting once more. I find that since I spend so much time thinking about storylines I've come up with during the day, I will process a lot of details at night while I'm sleeping, taking a quick trip to places that only exist in my head. Unfortunately, I can't remember many details of these dreams, but it "settles" things in my brain, allowing me to cough up TONS of pages of script in a short period of time. In a lot of cases, I end up writing kind of stream of consciousness and then go back and format in some way. The results sometimes are a bit chaotic, but from time to time, I end up with a little nugget of gold.
So, recommendation to everyone out there... Dream or daydream, resting or napping, sleeping or tossing and turning, if you have ideas, get them written down no matter where the source. I haven't tried writing when I'm feverish because I haven't been that sick since I started writing again, but next time I am, I'm going to see what comes out!