Probiotics won’t necessarily cause die-off immediately, but they can certainly cause nausea in some cases. The reason is that the probiotics start changing the composition of the gut flora. In the short term, that can lead to gas, bloating, and nausea as your gut flora adjust. Starting with a low dose of the probiotics might help to avoid this.
Of course, the other alternative is that you’re having a reaction to one of the ingredients in the probiotic. That seems unlikely though. Maybe give it a few days and see if it continues?