Slight backstory - I get the same bus at the same time every day, across my city to work. I recently noticed a man who also gets the same buses, who seems to look at me a lot .. (Um, to be fair, I may have been looking first. Just a little bit.) We have exchanged glances, smiles and a brief moan about the British weather. Since I've noticed him looking for/at me, catching me looking and grinning etc I've gone from normally functioning human being to all dry-mouth, heart pounding full on crushing. I feel like an utter utter twat 
Now I just kind of scuttle off the bus in case I get the urge to talk to him (far too embarrassing), when he does smile I go all weird and do this awkward robot grin so he probably thinks I'm a freak.
I have no idea if he's just looking at me to see if I'm looking at him, if he's looking because he thinks I'm stunningly attractive (v doubtful at 7am), if he's terrified of me so checking where I am so he can run in the opposite direction, but all the glances and smiles are Doing My Head In.
WWYD? Would you ignore? Make conversation to make it less awkward? Hijack the bus and refuse to release the passengers until he explains why he keeps smiling at me?
I'm crap at this stuff. WWY, a normal human, D?