Firstly, starting last month, I have a colleague seated directly across from me who keeps up a constant muttering/whisper throughout the entirety of the working day. It's what I would describe as an inner monologue (similar to what I'm half thinking while working, 'oh no this part goes here' or 'right then, now I just need to save this and then...'). I'm having trouble in that I'm finding it really very distracting.
More context is that we work in an office (not customer facing if that's relevent), and the work we do is time sensitive. We're targeted quite strictly and they're not easy to attain even when working full pace (or at least that's how it is for me). I am slightly more senior than he is, but only in the sense that I deal with the more complex version of the same type of work. I am permenant staff, he is with us through an agency (this is relatively normal where we work, they have been with us for more than a year now and will be for the foreseeable future).
For context my colleague is autistic (he chose to tell the team this himself). I have heard another member of our team being unkind about his constant talking before, but I have been a coward and not said anything to them directly and just told the line manager. I don't know if he has also heard this but I'd guess that it's likely. With all this being the case, I don't want to cause him any more trouble if possible. In fact in some ways it's easier than the woman who sat there previously, who talked almost as much and also wanted my attention. At least he doesn't mind that I'm trying to concentrate on my work and not on him.
It's been two and a bit weeks now and so I am slowly learning to tune this out. But the second and main thing I am finding troubling is that when things go wrong with work (say, for example the systems are going slow or delete rather than print a document - not uncommon with our ancient systems sadly! A lot of little things go pear-shaped every day) my colleague will raise his voice suddenly and seem to shout the same inner monologue, this time about what is going wrong and his frustration, and sometimes strike/slam the desk/keyboard quite hard. This happens about once every hour or two.
I know it sounds silly, but it really makes me jump every time, and it's making me really dread going in in the morning. So my AIBU is this, would I be unreasonable to talk about this with my colleague? I am fully prepared to be told I can't and need to suck it up. If it would be okay to bring it up, how could I best phrase that I find it very distracting/frightening?
I don't think it would be possible for me to move desks due to how overfull the main office currently is, and how carefully the seating has to be arranged for our equipment. Sorry about all the brackets, I'm not very good at writing things like this.