The abrupt onset and cessation of magnetic reconnection has been a long standing puzzle, and is likely an important factor in turbulent plasma systems. We discuss three-dimensional (3D) magnetic reconnection with a guide magnetic field. We show the first 3D laboratory example of onset and stagnation of magnetic reconnection between magnetized and parallel current channels (flux ropes) driven by magnetohydrodynamic (MHD) attraction and a kink mode, which is a 3D plasma current driven instability. Antiparallel magnetic field lines carried by these colliding flux ropes annihilate and drive a reconnection electric field. We also show examples where the compression and line bending of a guide magnetic field results in bouncing flux ropes. For this case no reconnection occurs, but we measure an out of plane quadrupole magnetic field signature with no Hall effect. We outline a simple MHD theory to account for the existence of a threshold between flux merging-reconnection and flux rope bouncing. This threshold and the accessible dynamics may be important for 3D dynamics, turbulence, and magnetic structures that become filamented on ion gyro scales. Schematic of the Reconnection Scaling Experiment with fast camera images taken along the dotted line of sight, showing two and three flux ropes that sequentially form, attract, collide and merge.