2009 Chevy Tahoe - When I am stopped, and push on the gas, the car will not go

I have a 2009 Chevy Tahoe with about 200,000 miles.  In the past 4 - 5
months, on about 7 different occasions, the car does not go when I push on
the gas.  What I have done is shift to N and them back to drive.  When doing
this works, the car jumps forward and then goes.  This morning I was at the
light, it changed, I pushed on the gas and it did not go anywhere.  I did the
N/P back and forth a few times and it went just enough to get off the side of
the road.  Each time it makes me a nervous wreck and I have to put my
hazard lights on. I have had it checked a few times but the problem is that it
does not happen all of them time and I guess at this shop, it needs to be
something that happens for them to correct.  I hate to think that I need to
take my truck to the dealership but maybe pay the fee to have it determined
what is actually wrong.