Well I have a chiwawa/terior she is7 and she is always playful she was fine in the morning when I left and I came back she was fine but then I went to do something and when I came back she was scared her tail was up but she followed me every were and she sometimes shakes help

When a dog is afraid the tail is usually down between their legs. Why do you think she is afraid?

Maybe something happened when you were gone she might have heard gun shots or something went wrong when you were gone. Possibly if there was someone else in the hous that might have put a bag on her head hit her or abused her