Any tips for transitioning through the four month sleep regression? Reducing the startle effect now that we can almost roll over?

Baby girl is 3.5 months and started to sleep 7 hour stretches starting week 8. Now at week 15 she is waking up to feed in the middle of the night and fighting all her naps. She also moves violently in her sleep and wakes herself up.

What are some things that helped your baby 1) sleep longer 2) sleep well?