Hiya,
when I was first pregnant (this time - not the others) I would wake up feeling very sick - like you it passed after about half an hour. I just lay in bed waiting for it to go away.
I think it was my insides 'waking up' as they tend to settle when you are asleep...and the uterus pressing on, or affecting, the bowel close to it, which in turn made me feel sick as things were moving differently to normal.
What helped me a bit was eating last thing at night, so my stomach wasn't empty - and also I took medication before going to sleep, which I was taking anyway for the same thing, I just took it a bit later than I had been doing.
I found that this feeling came and went, and was something I could anticipate and deal with, in a sense - much more than the other type of feeling sick, which was more like a sensitivity to smell and would happen throughout the day, but went away at night. That's caused by your hormones - you might not get it, I hope you manage to avoid feeling too bad.
But certainly I remember that physical sensation of feeling sick when I was about 4 weeks pregnant - it probably eased off after a week or two, as I said, coming and going now and again till the second trimester.
Good luck x