Best thing I can tell you about chicks at 2 to 3 weeks old is that they are all instinct right now. And those instincts are important for survival. Any large thing is a perceived threat. Anything reaching toward them is a threat. It doesn't matter if they see you every single day. It doesn't matter if you have yummy treats, they are still learning about what is yummy and what isn't. Don't ever stand over a chick, or try to reach down and grab one. Always move carefully, at a low level. Keep hands low and slow.
They are too young to be allowed to freely run around. They need a chick-safe pen, small enough for you to gather them up when playtime is over, but big enough for them to really stretch those legs.
It's a big reason why the coop and run should be done and ready before you even get chicks. Makes things easier on them once they are ready to move outside permanently, and it's a safe play area for chicks where you can more easily catch them.
In time, as they get older and bigger, they become less concerned about everything trying to eat them. By 4 weeks old, they will begin to see you as a source of good things. By 6 weeks, they may be running to you for treats. By 8 weeks you may have to shoo them away from your feet to walk.