I just got on table, no reads on villain. Should i laydown here, also should i have 4bet pf?

Full Tilt No-Limit Hold'em, $1 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Button ($74.15)
SB ($141.50)
BB ($109.55)
Hero ($99)
MP ($261.30)
CO ($72.75)

Preflop: Hero is UTG with J, J.
Hero raises to $3.5, MP raises to $12, 4 folds, Hero calls $8.50.

Flop: ($25.50) 6, 2, 5 (2 players)
Hero bets $18, MP raises to $249.3 (All-In), Hero???