2018 trans slip

I just bought a 2018 tundra trd off road sr5 5.7l v8. I've noticed after I start it either morning, night, or mid day it slips a little making a thud feeling/sound going into 2nd then it wont do it again. It has 600 miles on it, is this just breaking it in or the begining of a bigger problem? I debated on taking it back and having them look it over but I know its going to be one of those things that wont happen once I'm at the shop. Any advice?

 

sure it's not the ABS self check? I think it happens at 12 MPH if I remember correctly. It'll only do once per start-up.

 

Abs check almost at the same time it locks automatically

 

Thank you guys I just found a few more threads on here once I searched the abs sensor so I'll just delete this one. I got home and threw it in manual mode and it did it with no shift around 13 mph. You guys saved me a trip and hours of mechanic bs