I used to spend most of my day every day speaking German (my work environment was 100% in German) - it did a lot to degrade my accent in English, at least for the time I had that job. I also worked with kids, and when they spoke to me in English I'd have to respond to them in German, so when I'd get off of work and have someone talk to me in English, I'd often respond in German.
I do have an "autist" accent though - just strange word emphasis, strange voice tones, and a decent amount of gibberish and words that, unless you know me well, have no meaning. There are also times where I say the same word over and over but have multiple meanings. Often it's nonsense words, for example "darp darp darp darp darp darp" or "dur dur dur dur dur dur" or something like that. I'll also roll R's and things like that with it sometimes, and hold the rolled R.