After college, I had a NEET period of roughly 6 months. I would see friends maybe once every other week because I was somewhat depressed about not being able to find a job and had to be dragged out of the house, and the only people I spoke to regularly in person were my parents. I went to my first meetup (for programming) towards the end of that period before getting my first job, and I felt all of the stuff you described.

It was really jarring, but I knew what was going on, so I didn't freak out. I'd read about how solitary confinement affects peoples' intelligence, especially their ability to formulate speech, and I figured I had a diminished version of that which only took effect when talking to strangers. It took about a week of work and interacting with people other than my parents on a regular basis for me to feel normal again.