2008 Auto Transmission

My apologies if this has been answered before (I could not find it any of the previous threads). I have a 2008 Impreza with an auto trans and it shifts kinda odd now and then. It was in an accident before I bought it and wonder if that has anything to do with it or is it an overall transmission deficiency? I've driven standards before this and am kinda new to this situation. Any ideas? A local parts guy suggested a Lucas Oil Transmission additive to help with shifting. Is he right or just full of it?