u/Saeko_The_Axolotl

Hey so for context I've had my dog (Who is a Poodle x Collie mix) since he was 12 weeks old, now he's 5 months, and he flinches quite often when I go to pet him. However, I've never hurt him, hit him, ect. I'm quite worried because I saw on a science program a few years back that dogs don't flinch unless they know pain might be coming? I'm not sure what to do, none of my past dogs have done this.