This happened to me once when I was on the subway around 2:00 or 3:00am. This guy next to me was mostly asleep, and every now and then he’d have one of those moments when he picks his head back up because he’s falling asleep too much. By the end of it he was definitely leaning on my shoulder to a degree. Luckily for me he didn’t smell bad, because that would’ve sucked. All I could think of at the time was whether or not he was going to fall down once it finally got to be my stop and I got out of my seat. He didn’t fall down when I got up, instead it just woke him up. I was still afraid I wasn’t going to be able to get up without him smashing his head though.