Learn Spanish (Spain): Durante el verano trabajo en un hotel.

The "I" is built right into the verb. Trabajo means "I work". You could say yo trabajo, but Spanish speakers usually drop the yo because the ending of the verb already makes it clear who is doing the action.

Doesn't trabajo mean "job" instead of "I work"?

It can be both! El trabajo is a noun meaning "the job" or "the work". But trabajo is also the "I" form of the verb trabajar (to work). You can tell it is the verb here because there is no article like el or un in front of it.

Why use en here instead of a different word for "at"?

The preposition en is very flexible in Spanish. It covers "in," "on," and "at" in English. When talking about a location where an action happens, like working at a hotel, en is the perfect word to use.

How do you pronounce hotel in Spanish?

The letter "h" is always silent in Spanish, so you pronounce it starting with the "o" sound. Also, the stress goes on the last syllable: oh-TEL.