Yes, it's not uncommon for individuals who have been in relationships with narcissists to develop some level of paranoia or heightened vigilance when interacting with new people. This can happen because they may have experienced emotional abuse, manipulation, and gaslighting during their previous relationship with a narcissist.
Being in a relationship with a narcissist can be incredibly draining and damaging to one's self-esteem and emotional well-being. As a result, people who have been through such experiences may become more cautious and hyper-aware of potential red flags or signs of narcissistic behavior in others. They might constantly look for clues and try to analyze the behavior of new people they meet to protect themselves from being hurt again.
While being cautious can be beneficial to avoid getting entangled in another unhealthy relationship, it's essential for individuals to strike a balance between being cautious and open to new connections. If the paranoia becomes too overwhelming and interferes with forming healthy relationships, seeking professional help such as therapy can be beneficial to process past traumas and develop healthy relationship patterns.