When it comes to rhythmic issues on the saxophone, you know you’re on top of the fingerings and the sound, but you start a phrase and then you either rush or drag, or you choke on the long tones. This is almost always because your body loses the pulse as soon as you have to think about air (or fingering), so think of the pulse as a bodily function, like walking. If your body doesn’t stop walking, your notes shouldn’t stop, either.
Most folks try to count, but that’s not reliable; use movement instead (foot tapping, gentle swaying, pulse in the stomach). You don’t want to look like a spaz, just to have enough movement so that you can feel it even on long tones. On a long tone, try to feel the pulse within the tone so that you don’t float.
One of the biggest problems is that you squeeze up when it gets hard and you lose the pulse altogether. When you squeeze, your notes are not smooth, so loosen up and simplify (play only the first note of a group, for example, or half the tempo), but keep the pulse going in your foot or your body. This will teach your body that the pulse is more important than the notes, and you won’t have that herky-jerky feeling anymore.
Try this for a few minutes a day: clap or speak the rhythm of a melody before you pick up your horn, then play the rhythm on one note. Then play the melody with the correct pitches but the same rhythm. Do this for maybe fifteen minutes a day and it will help your body understand how movement and sound are related, so you can concentrate on the fingerings if you need to.
If you still float, try playing along with a metronome and recording yourself. I’ll bet you’ll find that you’re floating before you think you are, especially after you take a breath or play a long tone. Figure out where you need to breathe so that you can keep the pulse going even through the rest. Rhythmic playing is not about counting so much as it is about feeling a pulse and having it propel your music.