Kiarra
Former Betta Breeder
It could absolutely be part of it. Temperature fluctuations can drive these little guys nuts. Sometimes it's better to have no heater at all, than to have a heater that fluctuates so badly.
If your room temperature usually stays pretty stable, and doesn't get cool, then you can probably ease him off the heater and just go without. However, if the room temperature fluctuates as badly as the tank temperature, it's probably time to buy a different heater.
This could solve your problem entirely, as it is possible that this is what is causing him to stress out and eat his tail. But it's also possible that this is just a contributory factor, and there's a larger problem, or a bunch of small problems, contributing to his behavior. Regardless, it's worth a try to stablize his temperature as much as you possibly can.
If your room temperature usually stays pretty stable, and doesn't get cool, then you can probably ease him off the heater and just go without. However, if the room temperature fluctuates as badly as the tank temperature, it's probably time to buy a different heater.
This could solve your problem entirely, as it is possible that this is what is causing him to stress out and eat his tail. But it's also possible that this is just a contributory factor, and there's a larger problem, or a bunch of small problems, contributing to his behavior. Regardless, it's worth a try to stablize his temperature as much as you possibly can.