But the Spirit himself makes intercession for us with groaning which cannot be uttered. I always hear this verse interpreted to be a referece to praying in tongues, but it does not seem likely that tongues are in view here simply because tongues can be uttered, yet these groanings cannot. Please also clarify to whom the Holy Spirit intercedes. This verse seems to teach a plurality of persons in the Godhead, not the view of Oneness Theology which says the Holy Spirit is the same person as the Father. Also, the text says specifically says that the intercession involves groanings , without any mention of tongues.
Language is intelligible, while groanings are unintelligible.
For these reasons it does not appear that Paul had tongues in mind when he penned this verse. Now concerning the explanation of this passage from a Oneness perspective, we do not see this passage as indicating that the Father intercedes with Himself, nor as indicating a plurality of persons within the Godhead. Such a view is very tritheistic, and lends itself to the notion that one person wills something the other does not. It also lends itself to the notion that one person of the Godhead could know something that another person does not. Such is even contrary to Trinitarian orthodoxy.