Is it usual for people's behavior to get a little bit weird if they spend too much time alone?

I cope better when I have family and friends to talk to. I do enjoy being alone for short periods.

I agree that people who are isolated for prolonged periods drift toward “feral” behaviors. But how can you decide whether this “loss of inhibitions” is the result of insufficient interaction with others or an attitude of “I won’t see em again. Who cares what they think?”

No clue. Never had enough time alone to think about it. After 37 years with my wife, two kids and now grand kids alone time is at a premium for me. Even back in the day, I always had a girlfriend or buds hanging around.
When I am alone l like to sit in the yard and enjoy nature. I know that when we lived in the country I would sometimes talk aloud to myself if I had time to go explore the woods or go fishing at the tank. Like, Take my worm you little bastards I know we have fish in here. Or if I noticed a snake I might exclaim, wtf was that? Is that abnormal? Never thought much about it really.

Extended periods alone requires an alternate behavior. Alone means entertaining oneself, keeping the mind active.
This would be a tough habit to break simply by being around people again. They are used to conversations going forward at a pace. They could interrupt without thinking, change topics, or walk away. They are accustomed to being each faction of “interaction” so awkwardness should be expected. On the other hand, they could seem completely withdrawn, because the DON’T want to cause things to skew. Also, they could be very quiet, just because it is so cool to hear and observe others for a switch.
Facial expressions would lessen over time, so they could appear completely disinterested when they are actually amused, or enchanted.
There are several simple differences which could seem bizarre to the observer.

Yes, definitely. I used to work for my dad’s small business and it required me to work 8 or 9 hours at home. I already suffered from social anxiety, so sometimes I didn’t have a genuine conversation with a stranger for weeks at a time. At most, I would mildly acknowledge waiters and cashiers whenever I went out to lunch or dinner with family.

My family noticed that my social cues were completely off, and that I was starting to develop signs of agoraphobia. Luckily my mom encouraged me to see a therapist, and I underwent exposure therapy, fortunately stopping a destructive cycle before it got worse

applause
Good for you, @rockfan. I’m glad you worked it out.

I think so. The same thing happens to groups that are removed from society for too long

Social skills will eventually get rusty if left unused for a long time. However, I believe that introverts tend to have more resistance toward bad effects that plague people who isolate themselves for too long.

Also, there could be a type of physical isolation where you can still interact socially with other people without disrupting your self-isolation. In that case, your social aptitude won’t degrade.

I get weird if I spend too little time alone. It’s the classic hurdle faced by any introvert – the need to balance social interactions with copious privacy.

Everyone has to sleep before a busy, productive day, and then sleep again when it’s over. Similarly, I need to buffer my people-time (which I enjoy immensely; I’m not asocial) with alone-time, to regroup and recharge the “batteries.”