What kinds of things might trigger type 1 diabetes?

I think I might have diabetes. I’m going to go to the doctor real soon. Until then I have a question i’d like answered. Can anyone tell me, that has type 1 diabetes, what lead you to believe you have it, like i researched a little bit and most of the things said alot of time people get had an illness of some sort that triggered it or something. Any help is greatly appreciated. Sorry about the bad grammar and punctuation.