The description of the Warp Drive in Star Trek:
Warp drive was a technology that allowed space travel at faster-than-light speeds. It worked by generating warp fields to form a subspace bubble that enveloped the starship, distorting the local spacetime continuum and moving the starship at velocities that could greatly exceed the speed of light.
From the Warp Drive article in Memory Alpha, emphasis by me
Is it possible to create a subspace bubble and therefore basically entering Warp but standing still? And is it possible to fly backwards / sidewards in the Warp or are there technical restrictions preventing that?
That would IMHO open some interesting tactical possibilities, specially the flying backwards. One could perform the "inverse Picard Maneuver" and therefore briefly vanish from the enemies sensor.