Learn Turkish: O bile toplum içinde çok sıkılgan.

It is formed by adding the tendency suffix -gan to the verb root sıkıl- (from sıkılmak). This suffix attaches to verbs to create adjectives describing a person's habit or natural tendency. Here, it turns the action into a personality trait: someone who frequently feels shy or uneasy.

Since sıkılmak usually means "to get bored," can sıkılgan also mean "easily bored"?

Technically it could, but in daily Turkish, sıkılgan is overwhelmingly used to mean "shy," "timid," or "bashful." The verb sıkılmak doesn't just mean "to get bored"; it also means "to feel squeezed, constrained, or embarrassed." The adjective sıkılgan draws heavily on this second meaning, especially in a context like being toplum içinde (in public).

Why use the compound toplum içinde instead of just saying toplumda?

While toplumda means "in society" in a broad, general sense, toplum içinde literally means "inside society" and acts as the standard set phrase for "in public" or "around other people." It's built as a standard noun compound: toplum + iç (inside) + possessive -i + buffer -n- + locative -de.

Why does bile come right after O rather than at the beginning of the sentence?