"He always seems to look worried, or wary, ill at ease."
He kinda' does.
But when you have people, and enemies, on the left, right, in front and behind, so to speak, watching carefully your every move, gesture, and harking to every word you say because you may well become the Prime Minister - and there are many who would prefer that not to be the case...
... it's hardly surprising.
I'd be wary, too - and probably look shell-shocked on a permanent basis. In fact, I'm amazed anyone wants the job at all, considering the state of general dis-satisfaction - and division - among the general public. I mean, where do you start?