Yes, it is normal for betta fish to hide. I always encourage betta owners to include a decoration or little cave for their betta to retreat into. It gives bettas a safe spot where they can feel secure when they need it.
While bettas may hide for any number of normal reasons known only to them, there are a few things to consider, just to be sure nothing is wrong. If your betta is hiding to escape a strong current in the tank, you may want to take steps to reduce the filter flow. Bettas prefer lazy currents, and strong filters may stress them out.
Take a good look at your betta when you can and assess his condition. Look for injuries, torn fins or signs of disease. While a lazy betta is no big deal, you want to make sure there isn't some other issue.
If you have other fish in your tank, you need to make sure your betta isn't hiding because he is being bullied. A lot of people worry about bettas hurting other fish, but more often than not it is the betta who ends up in danger in a community tank.
In addition to hiding, you may also observe your betta resting on the gravel or plant leaves. This too is normal behavior and nothing to be concerned about.