When I set two keyframes, the object moves from a to b according to the type of keyframe, like starts fast/ ends slow.

However, when I set three or more, the object hesitates at each intermediate no matter what the setting.
e.g. a spaceship "flying" through the air curves nicely through the keyframe but it slows down at that spot. I've tried linear, smooth, etc. All seem to do it.

The resulting motion has hiccups.

P.S. Any way to see the path the object takes?