What subtle signs did you notice was autism?

Hi everyone! I have a 6(m) who is in kindergarten (US). He is diagnosed with ADHD and is currently medicated for that. It has helped wonders with his emotional regulation and other ADHD behaviors. However, I have always wondered if he also has autism. He has some behaviors that make me question is it ADHD, or is this autism. When he was around 3 or 4 (I don’t remember the exact age) he had a small autism evaluation with his pediatrician. I noticed no blatant signs such as hand flapping, or lining things up in lines at the time. He always had some sensory issues that over time I chalked up to his ADHD. But the line between ADHD and autism isn’t very distinct so of course I question if what he does now is one or the other. For example:

1. He will make eye contact but he doesn’t maintain it. It will last for a few seconds and then he will look elsewhere.
2. He will randomly clap as he’s doing things. Sometimes this clapping is quick and other times it goes on for longer than 10 seconds. He doesn’t realize he is doing it.
3. He will randomly attach himself to random words people say and repeat them. A person walking by shouted “hey stupid are you coming” and then he shouted “hey stupid” back.

This is what I have noticed so far that could be distinctive to autism and not 100% ADHD. So I’m wondering what subtle signs of autism did you notice in your kids before they were diagnosed?