What is the bulb? Bulb filaments take significantly higher currents at start up than when hot (up to 10 times as much) so you have to rate the transistor or MOSFET accordingly.
The IRF730 is an odd choice of MOSFET - 400V rating and far too high an on resistance (1 ohm) for a low voltage circuit. You need a logic level MOSFET with an on resistance perhaps in the 50 to 10 milli-ohm range (I'm assuming the 12V bulb is a automotive bulb needing several amps and you don't want the bother of a heat sink on the MOSFET).
MOSFETs rated in the 20 to 60V range will have lower on-resistances than high-voltage parts, all other things being equal.