What causes overlapping and shaky vision?

I have just started having the following symptoms and am wondering what’s wrong. When I switch the object I am looking at one of two things happen, sometimes both. First, if the object is a ways off it might take some time to focus on it. While trying to focus my eyes seem to get a little...distracted – that’s not the right word, but it’s close – and will flitter over other, nearby objects before settling on the one I’m wanting to look at (giving me the impression of shaky vision). Second, and most prominently, when I turn my head it’s as through my vision shakes a bit. Sometimes it’s as if it is taking a bit longer for my brain to interpret what my eyes are seeing and there’s this ‘bounce’ after my vision finds it’s target. Any ideas?