Z71 CC LB

I was sitting I my truck with it idling on a decent incline with the truck in park and suddenly I was rolling back wards. It happen twice in the same instance as I was waiting on a driveway to pick up my son. At first I didn't know what was happening but hit the brake and stopped, then lifted my foot and a few seconds later I was rolling down the driveway again. I also noticed a complete drop out or total loss of power when making a hard right attempting to merge with traffic. I have felt the drop out a few times all in the same conditions, hard turn and hard acceleration. The loss of power does not sound or feel like the tranny though. I don't feel it slipping or hear the engine rev when it happens. The rolling started yesterday the hesitation has happen a few times but definitely a few times yesterday. The truck is a few months old with about 3500 miles it. Any ideas?