Dizziness is a common side effect of Zoloft It also lists vertigo as an infrequent side effect.
I would advise to re-consult your physicain for a re-evaluation of your medication.
I was on Zoloft for several years and had a really good experience with it. When I first started I had some dizziness and nausea but they passed and those brief, uncomfortable symptoms were well worth the long-run benefits of no longer being depressed. If you've only been on the meds for a short time, you might want to keep at it for a couple weeks. The side effects wore off for me in about 2 - 3 weeks. Good luck.