Then you're not staring at him. It's accidental conversation. Offer to drive without being unkind or sarcastic. Don't freak out about stuff you lived through in high school. Your son may not be as social as you and he may not call people.
Freshman year is hectic mentally.
There's a absorb into a 14 or 15 year old mind. Do freak out about some stuff. If he fits the Charter commercials for drug use, call me. If he's not making it emotionally, don't delay in calling me or someone who works with the mental health of teens. If he's acting out violently, call me at home.