Runs perfect then stalls

At least three times out of the week this happens to me while headed to work (happens when I am at least going under thirty five), I am driving and everything is perfectly fine then all of a sudden my truck stalls while still being in drive, I step on the gas and all that moves is my rpm gauge, my speedometer does not move at all. At this point when it happens I have to pull off to the side put it in park wait thirty seconds or so put it back into drive and everything works fine like nothing ever happened. After that happened I took it to a little local shop and they said it doing that because a faulty brake switch. Not sure a brake switch would do that or not. Any help would be greatly appreciated. Thank you.