You say it clicks over, I assume this means that it opens momentairly? If it is a 12V relay, and your voltage is dropping low enough to close it (typically 5-6 volts), then you have some other much larger issue that you should solve.
Have you tried a different relay? Is it possible the relay is bad? What source are you using to drive the coil on the relay? Are you sure there is enough current capability to drive the relay?
You can use a voltage divider to get the current down, but you would have to use very large high current resistors, an it would generate a good amount of waste heat. Really you should solve whatever issue is causing your relay to flicker, before it causes even more damage.
Also, perhaps explain a bit more about how your M2 is electrically connected? (Eg: Why you need the relay)