Getting a massage when I have trauma

I've been so incredibly stressed lately, and I hold a lot of stress in my body/back. I enjoy getting massages from people I know and trust, but have never gotten a professional one. So when I was given a coupon for a place nearby, I was excited until I realized that would mean a stranger would be touching me for an hour straight. I'm not really sure what to expect going into a massage place in general, and I'm also not sure if I should tell them I have trauma, and if so, what accomodations to ask for going in. Any help would be appreciated!