I've always used a starter, and almost all of my planes have had plastic spinners, at least at one time or another.
I've never had a spinner break. Do you get your starter spinning and then jam it against the spinner? Could certainly cause the breakage.
98% of my landings are deadstick... mostly due to fuel starvation.
Unless you mean an empty tank, then you're running your engine(s) too lean. I don't think one out of 30 of my landings are dead stick.
Dennis-