There isn't much to worry about here. Even if you hit moderate turbulence with no warning (and note that what is called 'moderate' will feel quite severe to you) the absolute worst case, one-in-a-million scenario for you would be bruises and breaks. There are a few turbulence-related accidents worldwide each year and these never result in serious injury.

The fact that the turbulence is unexpected won't have any consequence with respect to how the plane handles it. You certainly aren't going to die.