2nd to 1st gear? It also does it when I am accelerating between 1st and 2nd gear, but the jerk is not as noticeable compared to when its downshifting. Any ideas on what might be causing this?

your transmission could be slipping. try to do a tranny flush and fill it with new honda cert. tranny fluid

or it cld be ur torque converter if you do a lot of stop and go and hill climbing

if it is still under warranty-bring it back to Honda and they shld check it out and fix it b/c there should still be a power train warranty