There are a couple of free online drawing classes.
Some good general online drawing classes are drawabox.com and also ctrlpaint.com. Both are free and offer excellent drawing tutorials for beginners.
If you want something specific to life drawing, the Proko's Life Drawing class is awesome. Really simple to follow instructions, great videos, and he gives you specific "homework" to hone your skills. It is a one-time payment, but it's definitely worth it
Another one is newmastersacademy.org. Some of the best artists in the world have put together some amazing and insightful online tutorials. It has plenty of amazing content for life drawing and many other aspects of art. They also have a massive photo reference library as well. It is a subscription. I pay $30-$40 a month (I think it's gone up to $40-$50), but it is well worth it.
I've got heaps of other places I regularly go to in order to refine my skills, but those above would be best for life drawing.
Edit: Sorry I realized you were talking about 'in person' life drawing classes.
Most are really friendly and welcoming. Usually, you set yourself up and start drawing. Some studios offer life drawing classes where you pay a little more but they will have a teacher giving instruction and helping you refine your technique