Middle stages and M is between 9 and 20. AK or AQ in EP or MP.
Miss flop? Expect that either c-bet will get raised or check will get punished.
Hit the flop? Expect folds when you bet.
Odds of hitting flop are 3-1, pay off on hit = 2 to 1.
Your milage may vary, but the scenario is far too common to me as of late.
Position. Don't leave home without it.