Stalker is a beautiful movie but perhaps not the easiest one to watch, especially if you are not used to 10 min long shots of nature (e.g., water in a stream). Possibly Solaris, which you recommend too, would be an easier movie to watch first.
But yeah probably not easy if you’re not already fairly deep into art-house films.
You have to allow yourself to be immersed in it. It's a slower pace than commercial film makers adopt, but the atmosphere builds.
I find it so relaxing that I’ve just learnt to enjoy the whole experience and enjoy the dozing as part of the experience of watching the film.
Or mimoids.