B737 Captain reported failure of the stabilizer trim system during taxi. Flight returned to departure gate.

Narrative

I was last second re-assigned to work flight from ZZZ. I arrived to the airplane already boarded and the FO had completed all their preflight duties and FMC programming. Plane was boarded and ready to go. After I finished my checks we taxied out. I called for the before takeoff checklist on taxiway 1 going to XXL. When we arrived at the 'trim' item on the checklist. The FO went to set the trim to match the takeoff data. It was just slightly off. When He went to use the electric stab switch on his yoke it wouldn't move. I tried on my side and it also wouldn't move. We tried to adjust the manual trim wheel and it would maybe move a quarter turn before being stuck.We pulled off and called maintenance. Which they had us try to reset some breakers; and cycle the hydraulic systems. That did not work and we returned to the gate. When I asked the FO when he tested the trim system as apart of his flow; he stated it started off 'slowly' but then moved normally; at a normal speed. We were very very lucky this was caught before we took off. As we would've had no way to trim the airplane at all. I'm not sure if we would have been able to 'muscle' it back around the pattern. It seems like the motor must have seized just after the trim test. I know in training we did the stab runaway scenario; but i remember we had at least the manual trim wheel to use to help use control the airplane. In this scenario could we have brought it back around without any trim assistance at all? I would assume this has been tested in the simulator. We may have done it but I cant remember. Also is the motor designed; that when it seizes; we still have use of the manual trim wheel?