An occasional thought that flits by, dissipates quickly, likely not an issue. But by definition, "intrusive" means a thought that nags, disrupts, is unwelcome in frequency, intensity. It would be worth finding a therapist to get to the reason, the source—and to find better ways to defuse or address these thoughts. They aren't there "for no reason at all." With a clearer sense of the reason, you can seek better ways to address the root cause.
An occasional thought that flits by, dissipates quickly, likely not an issue. But by definition, "intrusive" means a thought that nags, disrupts, is unwelcome in frequency, intensity. It would be worth finding a therapist to get to the reason, the source—and to find better ways to defuse or address these thoughts. They aren't there "for no reason at all." With a clearer sense of the reason, you can seek better ways to address the root cause.