My 2004 Xterra sticks in second and won't accelerate.?

It has been doing this off and on for 6+ months. Two weeks ago it did it and totally stopped. It would not restart. I took it to the dealership and they said my timing belt broke. I assumed this was the problem all along. The day after I got it back it stuck in 2nd again. The speedometer sticks at zero and won't move unless a hammer on the dash. The car jumps/shudders when it sticks in second. At first I could just let it coast for a minute then press the gas again and everything would work. Now it won't accelerate at all. I have to pull over, turn the car off and start it again. The overdrive light flashes when I restart. I took it back to the dealership and also took it to a transmission only shop. Both places had it all day and could not find a problem. The issue is happening now at least once a week. I live in an area with lots of bridges, I am tired of being stranded on the side of the road and being so vulnerable in on coming traffic. I am about to pull my hair out. Does anyone have any ideas?