Is it common for braces to cause ridges to form in your mouth?

Possibly. If you mean "ridges" on the cheeks and lip tissues, then yes...The brackets can rub against tissues and cause irritation...Try using beeswax to smooth the edges.
Occasionally. Many people have the habit of lip or cheek sucking. Constant pressure of these tissues in and around the braces and wires can cause ridging; in time they will go away. Rarely if continuous through treatment, the normally soft tissue can become firm or fibrotic, again not a big worry.
Ridges in mouth. No it is not normal to get ridges in your mouth. Call and discuss with your orthodontist. There could be a number of reasons and most are not anything to worry about but discuss with your orthodontist.