I'm sorry, I'm sorry, I *have* to say it: you don't have to shave that hair! If you're concerned about hurting yourself, it might be a good moment to check in -- why do you feel like you have to remove your body hair? If this is something you're down to talk about, we should explore it!
That being said, different things make different people feel good; hair removal is certainly on that list. I have a couple of tips.
One: Use a (short) guard on your trimmer to ensure you don't nick yourself somewhere painful. Trust me, I've done it.
Two: Some people like to go upside-down or lay, legs splayed, in front of a large mirror to help them with shaving their perineum (the area between the anus and the scrotum and/or vulva).
Three: If you're able to, it might be a good time to make an appointment with a professional waxer. While waxing and plucking are a bit more painful (folks tend to report that you acclimate to the sensation over time, but it's not super pleasant), having someone with a good view & practice caring for the skin of the body can be really helpful. Some waxing salons will also offer discounts to first-time customers so that you can see if this is an option you're interested in.
I do think it's going to be a tricky area no matter what but making sure you're using a new/sharp razor and pulling the skin tight with your other hand, if possible, will help.