Well, you want to lerp between the actor and player from what I can see. If you don’t specify A, it will lerp from (0,0,0) to the player location and the Actor is probably not at (0,0,0)
As the actor (I’m assuming a crystal moving towards a player here) gets closer, it slows. It gives a nice effect.
If however you were moving from (0,0,0) and the player is at (100,100,0) and the crystal is at (30,70,0), it will jump backwards first before coming to the player and not necessarily in the correct direction. If the crystal was in (200,150,0) it would be more pronouced as it was always move from the same source point.
If you want a linear speed, capture the actor start location in the begin play to a variable and use that instead of the actor location to achieve a linear movement and you could adjust the timeline curve to ramp up and down the speed.