<<Disclaimer: Verify this information before applying it to your situation.>>
 
What works for me is to heat my oven to 200F for 5 minutes -- I start
it warming up as the very first thing I do, before assembling ingredients
etc.  Turn it off after 5 minutes.  By the time the dough is ready to
sit in a warm draft-free place, the oven has warmed up just enough but
not too much.  The bowl of dough doesn't need to be covered in there,
IMO, since I don't see how drafts or wild bacteria can get into the dough.
 
Obviously, this means you can't preheat the same oven to baking
temperature later on when the dough has mostly risen; this isn't a
problem for me because I have two ovens, but if I didn't I would
remove the mostly-ready dough and let it sit (covered) at room temp for
the 10 minutes or so that it takes to get the oven to 350F or whatever.