RPMs will spike all of a sudden as the transmission shifts from second to third gear?

Sometimes, when accelerating from a stop, the RPMs will spike all of a sudden as the transmission shifts from 2nd to 3rd gear. It jumps from say 2,500 RPMs to maybe 5,000 or 6,000 for just a second right before shifting. What's odd is that if it doesn't do this within the first few minutes of driving, it won't do it at all for the entire trip and the transmission will work as expected. It also may not do it for weeks, before it reoccurs. When it does occur, it always starts within the first few miles of the trip and will generally continue doing it whenever accelerating from a stop. What's really weird, though, is that turning the engine off and back on seems to resolve the issue. That's generally how I "fix" the issue when it starts; I just find a parking lot, turn off the engine, restart it immediately and the problem is gone for the rest of the trip. I had a similar issue this morning, but it happened for the first time at highway speeds. I made an earlier 20-mile trip with no issues, including on the highway. However, about an hour later when I went to return home, the transmission shifted just fine until about three or four minutes into the trip and about the time I got to the top of the highway entrance ramp. I hit between 55 and 60mpn and noticed it wasn't shifting into final gear. The RPMs were 4k. To fix it, I simply took the next exit, found a parking lot, turned the car off and back on. The rest of the trip went fine without any shifting issues.

When the problem first started happening a few months ago, I had a garage look at it. They said there's no shavings in the fluid and that looks good, but they said there was a code indicating maybe the Input Turbine Revolution Sensor was bad, so they replaced that. However, that didn't fix the issue. They don't really do transmission work but suggested maybe I just need a new transmission. I'm skeptical because in every case, turning the engine off and back on has resolved the problem. That seems to suggest to me it's an electrical/sensor issue. Am I off track here? Any thoughts on what it might be?