"Hitcher" is a dramatic monologue: its speaker is a separate character from the poet. This speaker is a frustrated man with a dull job, recounting what at first sounds like an unremarkable story about picking up a hitchhiker.
This first stanza provides some information about the speaker's situation. He recalls feeling "tired" and "under / the weather" before the poem's events took place. In other words, he'd been feeling sick—or maybe suffering from a more general malaise, such as dissatisfaction with his life. He had certainly claimed to be ill, as the "ansaphone" (answering machine) message in line 3 makes clear:
One more sick-note, mister, and you're finished. Fired.
The voice "scream[s]" this threat at the male speaker ("mister"), so it seems the speaker's work life had been miserable. A demanding boss had been hurling abuse at him and treating his sick leave with contempt. So the poem does begin with some tension—but there's no hint, yet, of the terrible event that comes later.
Caving to the threat, the speaker goes to work. First, he picks up a rental car, which he needs either for his commute or for the job itself. He "thumb[s] a lift" to the car's location, making him the first "Hitcher" in the poem. This detail sets up a subtle, but crucial, parallel between the speaker and the hitchhiker he'll soon meet.
Initially, the poem's language is as uneventful as the speaker's life. Line 5, for example, specifies the make of the speaker's rental car (known in the UK as a hire car):
A Vauxhall Astra. It was hired.
The speaker's tone sounds flat, perhaps even depressed. That full-stop caesura slows the line down, building an atmosphere of boredom and frustration. The car itself is about as average as they come: a small family car, common in the UK. It seems to symbolize the speaker's conventional, uninspired lifestyle, his role as a small cog in the capitalist machine. However, "Astra" comes from the Latin word for star, perhaps hinting at the speaker's frustrated ambitions—his subconscious longing for a brighter, more romantic existence.
Everything about this opening stanza, then, lulls the reader into a false sense of security. It also establishes the poem's form: quintains (five-line stanzas) in which the first and fifth lines are shorter than those in between, and the middle line is the longest. It's as if the poem is struggling to escape the constraint of its shorter lines—and sometimes bursts out of them, but only temporarily. Soon enough, this pattern will make sense in terms of the speaker's personality.
"Fired" (line 3) and "hired" (line 5) set up the expectation of a rhyme scheme, but the poem thwarts this expectation: there won't be another full rhyme until the final stanza. These two words are staples of capitalist work culture, in which people get hired and dismissed according to their usefulness and with little regard for their mental health. Subtly, then, the rhyme reflects the poem's broader social commentary.