Spokes break under stress, so the wheel is obv. being stressed in a way that overloads a spoke under certain circumstances. Do you care to share some more info about the wheel? Spoke count, spoke diameter, nipple material, hub brand, rim brand, specifically.

In any case, it seems unreasonable to keep breaking spokes if they rebuilt it recently. Take it back. You're a large guy, but not outside of the ordinary. I ride with plenty of guys that size who do not break spokes.