Этот персонаж сначала кажется спокойным, но позже вызывает подозрение.

Этот персонаж is in the nominative case because it is the subject of the sentence.

• персонаж = masculine singular noun
• этот = masculine singular nominative form of this

In Russian, words like этот change form to match the noun they describe in gender, number, and case.

So here:

• этот персонаж = this character
• both words are masculine singular nominative

If the noun changed case, этот would change too:

• этого персонажа = of this character / this character (accusative for animate masculine)
• этому персонажу = to this character

Because after кажется in this kind of sentence, Russian normally uses the instrumental case for the describing word.

So:

• кажется спокойным = seems calm
• not кажется спокойный

Here спокойным is the instrumental singular masculine form of спокойный.

This is common after verbs like:

• быть in some contexts
• стать / становиться = become
• казаться = seem
• оказаться = turn out to be

Compare:

• Он кажется спокойным. = He seems calm.
• Он стал спокойным. = He became calm.

So the -ым ending is there because the adjective is in the instrumental case.

Here кажется means seems / appears and agrees with the subject этот персонаж.

So the structure is:

• Этот персонаж кажется спокойным.
• literally: This character seems calm.

This is slightly different from the very common expression:

• Мне кажется, что... = It seems to me that... / I think that...

That version is more personal and includes the person whose impression it is:

• Мне кажется, что этот персонаж спокойный.
• This character seems calm to me.

You can also combine the two patterns:

• Этот персонаж мне кажется спокойным.
• This character seems calm to me.

So:

• кажется спокойным = seems calm
• мне кажется, что... = it seems to me that...

Russian often uses the present tense to describe:

• a character in a story
• a general impression
• a plot summary
• what happens in a film, book, or analysis

English does this too:

• At first the character seems calm, but later becomes suspicious.
• In the movie, he starts as a hero but later betrays everyone.

So the Russian present tense here does not necessarily mean the action is happening right now in real life. It can just be a neutral way to describe the character’s development.

If you wanted a clearly past narration, you could say:

• Этот персонаж сначала казался спокойным, но позже вызвал подозрение.

Yes, it is a very common expression.

Literally:

• вызывает = causes / brings about / arouses
• подозрение = suspicion

So вызывает подозрение literally means:

• causes suspicion
• arouses suspicion
• raises suspicion

In natural English, depending on context, you might translate it as:

• seems suspicious
• raises suspicion
• makes people suspicious

Russian often uses this kind of verb + noun combination where English might prefer an adjective.

Compare:

• Он вызывает подозрение. = He arouses suspicion / He seems suspicious.
• Это вызывает интерес. = This arouses interest.
• Это вызывает уважение. = This inspires respect.

Because in this expression, Russian usually treats подозрение as an abstract mass noun, similar to English suspicion.

So:

• вызывать подозрение = to arouse suspicion

This is the normal form.

The plural подозрения is possible, but it usually sounds more like:

• suspicions in the sense of several separate doubts or suspicions

For example:

• Его действия вызвали подозрения у полиции.
• His actions aroused suspicions in the police.

In your sentence, the singular is the most natural choice.

• сначала = at first / initially
• позже = later

They mark a change over time:

• first impression: кажется спокойным
• later impression: вызывает подозрение

You often see сначала ... потом ... in Russian:

• Сначала он молчал, потом заговорил.
• At first he was silent, then he started speaking.

In your sentence, позже works very well because it sounds a little more like later on than simple then.

So these are all possible, with slightly different nuance:

• сначала ..., потом ... = at first ..., then ...
• сначала ..., позже ... = at first ..., later ...
• сначала ..., а затем ... = at first ..., and then ... (a bit more formal/bookish)

Yes, the word order can change, because Russian word order is fairly flexible. But the original version is a very natural, neutral one:

• Этот персонаж сначала кажется спокойным, но позже вызывает подозрение.

You could also say:

• Сначала этот персонаж кажется спокойным, но позже вызывает подозрение.

This puts a bit more emphasis on at first.

As for the second clause, Russian does not need to repeat the subject if it is still the same:

• Этот персонаж сначала кажется спокойным, но позже вызывает подозрение.

The subject этот персонаж applies to both verbs:

• кажется
• вызывает

English works the same way here:

• This character seems calm at first, but later arouses suspicion.

You could repeat the subject in Russian, but it would usually sound heavier unless you want special emphasis:

• Этот персонаж сначала кажется спокойным, но этот персонаж позже вызывает подозрение.

That sounds unnatural in normal speech.

Спокойный is a broad adjective, and its exact translation depends on context. It can mean:

• calm
• composed
• quiet
• peaceful
• steady

In this sentence, calm is the best fit because it describes the character’s outward manner or apparent personality.

Examples:

• спокойный человек = a calm person
• спокойный голос = a calm / quiet voice
• спокойное море = a calm sea
• спокойная жизнь = a peaceful life

So here, кажется спокойным suggests that the character looks emotionally controlled or harmless at first.