As you enter the synagogue, be aware, above all, that the people in the synagogue, the congregation, are for the most part normal human beings, just like you. As a human being, you will understandably feel self-conscious. And they're normal, too. That means that, just like you, they are curious. Sometimes they are unintentionally rude.
People are always curious about newcomers.
When you see someone new, you also stare. Some of them are wondering who you are. Some of them are wondering if you have a place to eat the Sabbath meals. Some of them are wondering if they can help you, and some of them are wishing they had the guts to go over to the new stranger and introduce themselves and offer their help. For the most part, they really don't mean to make you feel unwelcome.