OP I think people have jumped a little too quick on this. I understand what your saying and Ive had a think about why that might be.
When I was a kid I had never seen someone in a burka. I grew up knowing (as a kid) is that if someone covers their face then its to protect their identity to commit a crime. A chap cycled past me last week wearing not just a helmet but a balaclarva and a face mask, the result was very scary.
I suspect the reason you felt uneasy, is that the human face and body gives off a lot of readable signals. We know if someone is friend or foe by reading their face and body language.
I think it was last year a judge ruled a lady to remove her burka (head part) while she was on the stand, I suspect the above reasons are why. How many times have you questioned if someone is telling the truth based on a raised eyebrow or slight smirk or rubbing their nose...Its simply not possible when the face is covered.
I did see a lady walking down a busy road last year wearing a burka and I have to smile because hers was short enough to see the stilettos. It was nice to see a bit of personality to connect with. When all we see is the burka, I realised that everyday as a part of human nature, we look at what people wear, what they like, their personality. Its a lot easier to strike up a conversation and feel connected.
How many times have any of us been out and complimented someone on their hair, jeans and got chatting?
I don't think your fear is based on racism.