kind/sort of think

“I kind/sort of think that you are making a mistake.”
Is this sentence OK?
Is “kind of think” or “sort of think” a verb?
I couldn’t understand it?
Please explain with full grammatical details.

It’s collowuial.
Formally it would be considered incorrect.

The speaker is either trying to be very polite about pointing out someone’s mistake, or is not absolutely certain that it is a mistake.

I kind of/sort of think = I believe that this is the case, but I am giving recognition that I might not be completely right about that.