While I hope its not the case, the gecko may be having a reaction to an accident during shipping. Usually any seizure-like activity will happen right after the injury occurs, and then the gecko will then appear sluggish and reluctant to move.
After years of being careful and lucky, I finally had a young leopard gecko jump off my body and land on the floor, resulting in an immediate seizure. I did what I could for her, but she died during that night. Yours may be fine. Time will tell; if she is ok for a few days - no more seizure activity - she will be unlikely to have any problems later that relate to this.
You've probably already set her up, but if you haven't then preheat the undertank heat strip and Place her on the heated side, with a hide nearby, and then leave her alone as much as you can. Feel free to check on her from a distance, but if you can leave her in dark & quiet, that's the best thing for her.
Quiet, warm, and dark.
Do not offer food if she's continueing to have seizures.
Talk to the person who shipped; accidents that affect shipped animals like this are very rare... but they do happen, even when the animal is well packed.
Best of luck to you and the gecko!
-----
Andrea A. 