What is your play?

Unfortunately I dont have the hand history but I will try my best to give an accurate description from memory.

Background: The players on the site are a mix of reasonable players and some very loose aggressive players (push with flush\straight draws etc) so sometimes it can be difficult to distinguish between the two types since a lot of the reasonable players love going all in with the nuts. No real reads on the villain yet but he pushed me off a pot the previous hand with an overbet that felt like a bluff (couldn't call because I didnt have much either).

Stacks:
Hero $60
Villain $120

Game:
$0.5/$1 NL 6-max (only 5 players at the table)

Position:
Hero is the dealer, Villain is BB

Hand:
I am dealt AK0 on the button and it is folded around to me, I raise to $4 and the only the villain (BB) calls. The flop is AQ8 rainbow and the villain bets $18 into me. What do you do?

I think you are in a push/fold situation here and the only hands that you can worry about are AQ, A8, Q8 and 88. If you feel he may be bluffing you then I would raise it to $40, knowing full well that he may push and you will have to call. If he has wired Q's you can always hope for the board to pair.