All good suggestions, I'm adding one more. Stretch your abs - not really hard, not bouncing or gaining flexibily type stretching, but just gently like you do when you get out of bed and yawn (or what you see a cat or dog do when they get up from a nap- just gets the stiffness out).

Lie on your stomach, push yourself up gently with your hands, hips on the floor. Hold for a count of ten, then do it twice more. Curling over a bicycle can tighten your ab muscles in bad ways as well as good, and cause back pain.

I also have a little muscle achiness at the beginning of the season, or when I would change my saddle/reach. After a week my back would get stronger and everything is fine.