Is the trinity biblically backed

I'm wondering where the doctrine of the trinity comes from, and I've only found that it stems from both Hellenistic philosophy (Platonism through Philo and Origen) and Babylonian polytheism (Nimrod, Semiramis, and Tammuz). It doesn't make sense for a triune god to be monotheistic. Has anyone else ever questioned its origins and come to a different understanding? Please let me know. I am specifically looking for instances of it in the Tanakh. (I am not looking for verses that have scribal errors)