Yes, more details would help tremendously in troubleshooting exactly what the problem is (if there is one). I know it's hard sometimes to accurately describe something, especially when you know the problem, but others are kinda guessing from patchy descriptions.
If you have the the Suburban water heater this may help, as I kinda have a feeling you may have the electric heating element on, and thus once the propane brings the initial water up to temp, then the electric element is maintaining it...thus why the propane doesn't NEED to come back on.
But here again, this is just a guess based off of incomplete data from the OP.
This FAQ link below could help maybe:
Suburban's electric switch and much more