I need to find a word for someone who you feel uncomfortable with - like awkward. Someone who you like, but can't really have a normal and comfortable conversation with. Maybe even someone who makes you feel self-conscious, though that's not what I'm really aiming for...
I used to work alongside such a person. He was okay, and acted friendly enough but there was something about him which made me internally cringe whenever we exchanged words. Perhaps it was his excessive enthusiasm that I found most irritating, in any case I always had an excuse not to join him for a coffee.
There are some people you do not want to be alone with, and not necessarily because you fear for your personal safety but because they are unnerving, and you feel uneasy in their company.
Her unnerving habit of touching people she was speaking to
uneasy: awkward or unsure in manner; uneasy with strangers.
inspiring nervousness or fear:
He was a huge, intimidating figure.
A courtroom is a frightening and intimidating place for child witnesses.
The trial in an adult court was severely intimidating for the eleven-year-old child.