I've experienced the two parts of waking up thing you were talking about many times. Sometimes it's a bit of a variation but the concept is usually the same. The main reason I had such an experience was because of a lack of sleep in which my mind would make up a whole bunch of reasons why I didn't need to get out of bed. So I would say that this is probably occurring because of a lack of sleep. If this is not the case then I would see a sleep specialist. I agree with what others have said, that you are experiencing hypnogogia but this reply is the reason behind why I think you are having this problem. If you reply could you please post your average sleeping hours in the week and on the weekend and the days this happens most frequently.
Thanks