Propane water heater shuts off

I have a propane water heater that keeps shutting off, when I check the unit it is in a stand by mode. If I turn the blower switch off then on about 6 times it will finally start working. The flame seems to be going out and when it does light the flame looks to be very erratic. Is this some kind of burner issue or flame rod issue? My tank is also at 50 percent, so I am not out of propane... Thanks!!!