Hip rotation stores and releases energy
Always be aware what your hips are doing
The more you rotate your hips toward vertical, the more energy you create and store, and the quicker you release this energy, the quicker you spin your hips the other way, the faster you go.
Propulsion is rotary (hips) not linear (arms) so...
Reset your hips vertical or a little past vertical, then start the stroke with hip rotation.