Sounds like my neighbour, and it's got to a point of being obsessive.
He is out and about in the garden, christ I haev seen him "dusting" his fence - everything has to be perfect, when he's deadheading plants he almost counts them meticulously, when he is doing something it takes hims like - all day? Even though it's just a five minute job for anyone else. He hardly ever goes out, and I never see many visitors, it's bizzarre, but also does my head in as everytime I go outside he's there shuffling around sneeky like - rain hail sleet or shine, and it freaks me out as I can't seem to spend time in my garden without him being there, and feel he's listening in to everything. Used to quite enjoy taking my phone outside and talking sitting on my garden furniture, not now - it's ruined all that for us.
The only think I could suggest is to tell him straight as this is the only way to make an impact - sure as hell if I knew someone like that and knew another person like me having to be his neighbour - and the stress it's caused me over the yrs, I would say to him ASAP.