There are two types of tramadol: Instant release and Extended release, and they are VERY different. I am fine with the instant release, but get headache, and had a serious problem with serotonin syndrome with the extended (mainly because of drug interaction).
Lower the dose for the first thing. I get along fine with 50 mg instant release twice a day. If you start getting leg muscle spasms (aka myoclonus) stop taking it immediately! That's the first sign of serotonin syndrome. But nausea is unlikely to have anything to do with that. Dizziness could be a side effect, but what's your dose? The tablets break in half easily.
What else are you taking? That's where I would look first with nausea.