I used to have a doppelganger around where I live. I had several incidents around ten years ago, as I'll relate, but the first time I became aware of my double was back in around 1996 when a friend of mine asked me where I'd been going one afternoon when he saw me driving out of our town. I was puzzled by this, as I'd still been at work at the time he saw "me". He told me that he'd seen "me" driving the same type of car and - spookily - it was the same colour.
Fast-forwarding a few years to 2003 / 04, I was in our local nightclub one evening when a woman came up to me, acting in a very friendly manner as if she knew me. "Oooh! Hello!" she said, putting her hand on my arm. I looked at her blankly. She studied my face a bit closer and then said, "oh. It's not you is it?". I just smiled and shook my head and she disappeared.
Soon after this, I was visiting my dad in hospital after he'd been admitted with heart trouble (turned out to be a medication issue and he was fine). A bloke and his missus were visiting an old gent who occupied the bed-but-one to my dad. I kept noticing the bloke who was visiting looking at me. I was starting to feel a bit nervous about it, so he came over, apologising, saying that I was the exact double of a guy he knew at work. He was looking because he was sure it was him, then telling himself that it wasn't... then having to look again to make sure. I told him that this wasn't the first time it had happened and related to him the night club incident. We had a laugh about it. I think he told me my double's name. It's a shame that I didn't take some notes and try to track him down for a photo opportunity.
Anyway, I've not had any doppelganger incidents for several years now. Perhaps he's moved away.