A8 Suddenly started tripping main breaker

[arjunsud]

After working fine for 2 years, suddenly, my hot tub Kees tripping the main breaker . To be clear, it does not trip the GFCI breaker outside the home by the hot tub, but instead the main panel in my basement .

Does anyone know why this is happening and how I can fix ?

Thank you !

[castletonia]

Can you reset the breaker or does it trip immediately once reset? 

[arjunsud]

I can reset it and it works for a while , then after different periods of time turns off .