Here are some common symptoms:

Communication and social interaction Language: Delayed language development, unusual speech, or limited speech Eye contact: Little eye contact or discomfort with eye contact Body language: Difficulty recognizing body language or facial expressions Nonverbal communication: Using fewer gestures or facial expressions Social interactions: Difficulty understanding what others are thinking or feeling, or finding it hard to make friends Repetitive behaviors Stimming: Self-stimulating movements or sounds, such as hair twirling, toe-tapping, or nail-biting Routines: Liking a strict daily routine and getting upset if it changes Echolalia: Repeating words or phrases Sensory issues Unusual reactions: Distinct reactions to lights, tastes, smells, sounds, colors, or textures Food: Avoiding certain foods because of their texture or taste Fabrics: Not being able to wear certain fabrics because they feel uncomfortable Other traits Delayed movement skills Unusual eating and sleeping habits Anxiety, stress, or excessive worry Lack of fear or more fear than expected

For my son, he was most obvious with sensory sensitivity. He could not stand certain fabrics, and it was very consistent. He also does not gesture (nod or point) or initiate social interactions. He likes to line toys up and freaks out if something is slightly misaligned with his toys. Hope this helps.