This happens to me all the time. Sometimes I'm cruising at 21-22 mph and another cyclist will sprint to pass me then gas right after and slow down so I'm playing leap frog with him. Triathletes training on the weekends tend to shoal at red lights when they see me as well and are surprised when they look back I'm on their tail coasting.

It doesn't bother me anymore though, it comes with the territory. It doesn't help that I look like a hipster kid. I guess it's good that I'm closing in on 30 but people think I'm 17.