Yes, occasionally. Nausea is the most common side effect. If you feel nauseated when you start taking the medication, talk to your doctor about taking a low dose for a longer period of time, so you can slowly get used to it. Smoking while taking Chantix can make the nausea worse, so reduce your smoking as much as possible, and quit as soon as you can.
Some people say they have trouble sleeping. You can help prevent this by taking the second dose of the pill at dinner rather than at bedtime. Other reported side effects include headaches, unusual dreams, gas, and changes in taste.
Medical review: Nathan Cobb, MD, September 26, 2017
Fiore MC, Jaén CR, Baker TB, et al. Treating Tobacco Use and Dependence: 2008 Update. Clinical Practice Guideline. Rockville, MD: U.S. Department of Health and Human Services. Public Health Service. May 2008.