Quote Originally Posted by User137
There may be some way with angles (slow perhaps) or i heard of some quaternions (i know nothing about)... or something else.
Indeed you won't get the right result by interpolating matrix values directly. You need to interpolate smoothly translation and rotation, which requires of separating your matrix into position and euler angles and then interpolating them separately. Look more on this here. You can also use and interpolate Quaternions instead.

By the way, here are two ]Linear Interpolation[/url] and Slerp.