is it doing this ON ALL roads? What Im getting at it could be the road crown and it's tendency to follow that pitch....It is possible your alignment is out, but 4,0000 miles and needing alignment is a surprise, UNLESS you hit some curbs...that could/would possibly throw your alignment out.
Take it in and have it checked out,let them know the car is pulling left/right.....Check tire pressures out before heading to the dealer and inflate to proper pressures, tire pressure chart is usually found on driver's side door jamb.
inflate when COLD.Keep us posted, good luck.
There are lots of things that would make a car "Pull" to one side, which is why I suggested checking these basic things first....also, take a close look at your front tire threads,outside toward inside, you should have pretty uniform thread wear going on,anything that appears exaggerated wear is a sign of alignment issues!