How can I smoothly interpolate between 2 position?
When you talk about bezier curves, it sounds like you think about them from an "illustrator" point of view, which is not totally right when it comes to spline interpolation (most probably what you are looking for).

Splines are piecewise curves that pass thrhough points. Bezier curves are third degrees splines between two points, and a series of them can form what "looks like" a single curve in a drawing aplication, but are actually lots of individual curves tied together (it counts as if the intermediate knots are doubled).

Illustration concepts aside, I think you could choose any 1-D spline interpolator from some popular library. I use Python, so I'd go with Scipy, take a look:

http://docs.scipy.org/doc/scipy/reference/interpolate.html#d-splines