2000 subaru outback ... first time this morning, I was stopped, started to go and there was a "thump" like someone bumped me from behind. happened several times from a start. What happening?

First thing is to check the fluid. Second thing is to consider getting the fluid and filter changed.

sounds like a broken motor mount, check to see if you have fluid under car where you park ,if not look atboth motor mounts.good luck aaacar

so the "check engine" light came on, then the AT oil light came on. I brought it in to my mechanic, it was put on a scope (?)..... it was some type of problem with a sensor.... good news, they fixed it, no cost..... I'm back on the road.... thanks for those who read and got back to me.