Any ideas?

This has only happened a handful of times and thought maybe someone had an idea. I'll be at a stop, and when I press the gas, it feels like the transmission or something in the drive shaft grabs for a second. After that, everything is fine. It did it today when I was backing out of a parking spot and when I put it in drive. Again, this only happened a few times.

sounds like your convertor may be on its last leg. Mine does that while driving, locks up like the TCM told it to lock up in the middle of a shift.

I've had the truck for almost 4 years and I can only think of maybe 5 times it has done this. It always drives and shifts great. And it only does it for a second, then it's fine.