It seems that on the weekends, when I'm sleeping over my friend's house usually, and sleeping in, I tend to get very vivid dreams. I feel like everything is really happening, and in the morning I really remember everything. However, I don't realize I'm dreaming inside the dream, it's like things just happening and me acting naturally. What's the deal with these dreams? I've only recently started experiencing them somewhat often (about a month ago, over the same friend's house I had 3 very vivid dreams in a row, and last night I had one).

*edit*
Now that I think about it, every time I would wake up partially through the dream, due to being cold. Is it possible that being really cold when I sleep causes this?