I am naturally a pretty social person and I love seeing people a few times a week if possible. But other than that, I like my alone time. And when I am having alone time, I prefer not to be disturbed.
That said, sometimes I go on social binges where I hop from hanging with one friend to the next to the next for a couple days or more at a time. I am usually utterly exhausted by the end of it, but no regrets. Then comes alone recharge time. Then time to do it again.
If I am isolating myself and not contacting my friends, it is because I am in a very low state of mind, and likely highly depressed. When I go into that mode, I push everyone away, and I hide. I don't like being burdensome on others and I will isolate until it utterly consumes me and nearly destroys me. Pretty much not good. Need to work on not doing that.