I start slow and always end up feeling better at the end. In fact, I often end up finishing a group ride before riders that are overall faster than me.
One of the reasons I stopped doing certain group rides is that they all go out like bats out of hell. DH and I have learned that on many of the shorter rides we do, we often start off climbing, go slowly, and by the time we get back to the flatter part of the loop, we can get our averages up about +2 mph.
If people think this is wimpy, well, it works.