They have Perimeter.
aka 'DeadHand'
It's an autolaunch system.
Yes, just like Dr. Strangelove.
http://www.businessinsider.com/russias-dead-hand-system-may-still-be-active-2014-9
There won't be time to retarget
A) Allegedly. I'm very skeptical that Perimetr actually works the way people claim it does, and offer as evidence the fact that we're still alive.
B) Even if Perimetr does work that way, the Russians would plan for multiple nuclear war scenarios, some of which might include re-targeting SLBMs. For example, there is speculation that one of their SSBNs was actually intended to take out an American carrier battle group - essentially by dropping enough warheads on the right grid square to ensure a kill. If that is the case, it presumably is designed for rapid re-targeting, and it's possible that other Russian SSBNs have the same capability.