I can't think of anything to say to people at work. If someone speaks to me to try to strike up a conversation all I can do is panic and say "haha yeah" or "haha no it's OK" and then nothing else. There's nothing happening in my brain, no instinct or desire to respond which then generates thoughts or questions to ask them. I can only politely sputter out some contentless yes/no response and then get away from the person. Then perhaps 4-5 minutes later when I have calmed down I can occasionally think of what I could have replied with, what a normal person would have said.