I do not typically place warnings on my fanfiction, regardless of whether or not the story contains commonly triggering topics. A warning for any particular trigger on my fanfiction does not necessarily indicate the absence of other commonly triggering topics. If you would like to know if anything I have written contains your specific triggers, squicks, or dislikes, you may contact me.
There is no standard list of commonly triggering topics. Some commonly triggering topics include:
Bondage
Child abuse
Child neglect
Death, animal or human
Drug trafficking
Drug use
Eating disorders
Genocide
Human trafficking
Incest, consensual or non-consensual
Infidelity
Mental health problems
Non-consensual sexual activity (rape, non-con)
Partner Betrayal
Sadomasochism, consensual or nonconsensual, with or without genital contact
Self-injury
Sexual activity with a person or persons with impaired judgment, under duress, or without clear communication of the intention to engage in sex (dubcon)
Sexual activity by those of some particular age range
Sexual dominance and submission
Sexual relationships between people of unequal status, e.g. student/teacher, parishioner/priest