When flying an SEP, I've sometimes been cleared to enter & backtrack, then given a takeoff clearance whilst backtracking to the start of the runway. In this situation, do ATC want me to continue with the backtrack, or turn around & take off from my current position?
Generally, if happy with the runway length available, once I hear the magic words "cleared takeoff", I just turn round & go. Noone has so far shouted at me for it.