Select the pen tool (g) then as you move over the vertex and you'll have the opportunity to draw out bezier handles on the motion path. You'll see the convert vertex tool, and sideways V appear. That's the tool you want. You can also select the covert vertex tool manually by clicking and holding on the pen tool in the tool bar. You can also hold down the Alt/Option key with the convert vertex tool selected to break the handles and operate them independently. Holding down the Ctrl/Cmnd key will give you a selection tool instead of the Convert Vertex tool that will allow you to move the vertex or adjust the Bezier handles. If you have a single keyframe selected in the timeline then you'll only see bezier handles on the two nearest handles. If you want to see all bezier handles select all keyframes in the timeline.
In your timeline example there are no bezier handles because the spatial interpretation is linear. You can create these sharp corners by simply clicking on a vertex that has bezier handles with the convert vertex tool selected.
thank you for the answer. somehow i didn't manage to save my earlier project and when i started a new one to test your tips, all vertexes of the motion path have bezier handles and i was unable to recreate the problem when the bezier handles where only on the 2 first vertexes. as i said, this issue keeps reappearing and disappearing for me. I'll save your reply on my notepad for future reference, thanks again