Is it normal to feel less interested in intimacy with others as you get older, but still enjoy time alone?

I’m 52 years old, and I’ve had great experiences in the past. Lately, however, I find that being with someone else feels more exhausting and less enjoyable than it used to. Oddly enough, I still enjoy spending time by myself and find it more relaxing. Is this just me? Is it an age thing? Has anyone else felt this way?