How old is your battery? A weak battery (or one that won't hold a charge) could be your culprit. The flasher uses a pretty significant amount of power, and at idle, the 1100 charging system is pretty ineffective, so that juice comes off the battery. After you get rolling, the bike's charging system is putting out enough power to allow the flasher to work. As the bike sits unused, the battery could be losing it's charge enough that after starting, there just isn't much left until it gets some miles on it again. You can get flashers that use less wattage, also, but that may be only masking a weak battery.