This happens now and then to my Honda Civic. There is really no specific thing that brings it on.
I don't think major replacements are called for just yet. It's just that something is a little misaligned and needs to be brought back into place.
For me, just having another person try it usually does the trick. Ask a friend or neighbor, or if need be, call AAA. Or try sliding it all the way in until you hear a click (or not all the way in and trying to turn it), wiggling it, maybe trying to move the key in the opposite direction before turning it in the usual one, nothing that will damage it. I wouldn't lubricate it, but maybe warming it up a bit (body heat? portable blow dryer?) would help. Or try sitting in the passenger seat and turning it from there, just to use a different angle.