Snug, I stretched in the darkness, waking as the thump of wheels slowed to the tempo of a heartbeat. I could sense that the train was approaching our destination, so shuffled down the berth, easing up the blind to find a ruby necklace of brake lights running parallel with the tracks.

It had rained overnight and the road was slick, the sky a midnight blue, a D-shaped moon fading in the corner. Dawn was minutes away, and I could just make out the jumble of houses on hills, lights flicking on as though fireflies lay between their folds.

I stepped into the corridor as the train curved around a lake that gleamed like a pool of pink metal as first light fell upon its surface. Around me, passengers were now zipping up bags, brushing their teeth and locking berths into place, pausing to look out of the windows as a pair of minarets rose into view like sharpened pencils. Istanbul’s skyline was coming into focus.

Five days earlier, I’d set off from London St Pancras hoping to retrace the original route of the Orient Express via Paris, Vienna and Bucharest, with the final leg passing through Sofia. Journeying 2,450 miles by rail, I now felt a deep satisfaction as the doors banged open and the sound of the second call to prayer greeted me on the platform. But I felt something else too: a rekindling of my love affair with night trains.

It all began in 2010, when I spent four months riding around on the trains of Indian Railways. At first the rail network represented little more than a mode of transport, a means to an end. But I soon realised that the trains possessed spirit and personality, each a character in its own right. As much as I enjoyed journeys by day – hot chai in one hand, fresh samosa in the other – and constant commotion around me, I relished the nights. It was after dark when I would find peace in the cool of the open doorway, talking to hawkers and ticket inspectors, making notes on the day gone by. As others slept, life beyond the carriage continued and I stayed awake to bear witness to it: a pack of pye-dogs being fed down an alley; bored drivers playing cards on car bonnets; the twentysomething winking at me from the back of her boyfriend’s moped as they careered towards the beach. Each moment felt like a gift, and while I hadn’t realised it at the time, I was already immersed in slow travel.

Three years ago, I made that jaunt from London to Istanbul, which involved three sleeper services: a shabby old Nightjet from Paris to Vienna; the surprisingly smart Dacia from Vienna to Bucharest; and the severely delayed Sofia-Istanbul Express. Three extraordinary journeys with wildly differing compartments, companions and scenery. Still, the madness of sharing with strangers, drinking whisky at 10am and trying to sleep to trance music was enough to spark an adventure that would take me from Palermo to Peru as I documented the resurgence in night trains.

Only a decade before, such journeys were fizzling out in Europe, the rise of budget airlines and high-speed rail leading to a cull of sleeper services. But who knew the world was going to shut down? After lockdown, rail travel began making its way back on to travellers’ radars. With climate change undeniable, people were keen to control their carbon footprints by exploring closer to home. Private companies, such as the Belgian–Dutch co-operative European Sleeper, popped up with plans to launch new sleepers across Europe, and existing operators – including Sweden’s Snälltåget and Austria’s Nightjet – wanted to extend routes, encouraged by campaign groups such as Back-on-Track and Oui au train de Nuit!.

With a bucket list of trains in hand, some of which were yet to start running, I set off to discover whether sleeper trains still held an allure – and who was using them. It didn’t take long to find out as I swept up the wintry backbone of Sweden on the Norrland night train to Narvik, surrounded by a cohort of school teachers from Stockholm on a skiing weekend to Kiruna in Swedish Lapland. In the din of a neon-lit dining car they offered me creamed cod’s roe on crispbread while explaining where I could chase the northern lights. They told me they regularly used the sleeper for weekends away, in both summer and winter, preferring the overnight ride to frantic queues at the airport – and the fraught disposal of liquids, they added, shaking bottles of wine in my face.

During the period of the midnight sun in Norway, I met Ludwig, a chief mate for the coastguard who commuted all the way to Tromsø at the northern tip of the country in a refusal to contribute to climate change. He had travelled the route more than 20 times and recounted his encounters with elderly women and happy drunks who shared their moonshine, presenting him with cured deer hearts in return for companionship. And on the Santa Claus Express in Finland, I tucked into smoky reindeer stew with my children, surrendering to the journey’s festive charms as snow fell around us, the train sweeping quietly up the country to the depths of Finnish Lapland, where the sun never rose and the howl of huskies carried across the treetops.

I found passengers travelling solely for the thrill of riding on a night train: on the Good Night Train from Brussels to Berlin, pouring out wine and beer; young families spread out and enjoying the space on the Intercity Notte from Rome to Palermo; and honeymooning couples loving the thrill of the Intercités de Nuit between Paris and Nice.

Of course, despite the romance of it all, I soon accepted the reality of being slung around as I slept, brakes wailing as the trains jerked to a halt in the small hours. Carriages were sometimes too hot or too cold, blankets too thin, pillows too flat, and companions just too damn loud. I’d sometimes wake with a headache, dreading the border crossings where I’d have to haul my bags or sleep with my passport in hand to make checks faster and more efficient. But all was forgiven during those moments of pure magic, when I’d nudge up the blind, eager to see where we were. Would the sun be firing streaks into the sky? Would the moon be hanging on? I’d sit in my blanket, coffee in hand, watching as farmers fed their flocks and children caught my eye from bedroom windows, a friendly wave never failing to make my day.

Even when we were delayed, no one seemed to mind – my fellow passengers shrugging, pottering around and enjoying the extra time to read, chat or snooze. Because time was what these night trains were giving us. Time to reconnect with friends as we moved through the darkness, with nothing but our own reflections in the window to distract us as we drifted into a state of confession, or opened up to family as though locked in a therapist’s room for the night. I had time for myself too, time to slow down and shut off, watching as the world whipped by my window and my thoughts calmed to a kind of meditation.

Since I began my journeys, new routes have opened, old routes have returned and the feeling is one of hope that night trains will stand the test of time. I don’t know what the future holds for them, but I know that when I board a night train and shift up to the window as we set off beneath the moonlight, it feels like coming home.

Monisha Rajesh’s new book, Moonlight Express: Around the World by Night Train (Bloomsbury, £22), is published 28 August. To support the Guardian, order your copy for £19.80 at guardianbookshop.com. Delivery charges may apply