We have a 1yr old chiuaua mix breed got her from animal shelter have had her scence she wa 14 weeks. And every once and a while she starts acting really skittish. Like she got into caffeen? But it happens a lot. And has probably scence she was 6 months old. It can be 30 min. or a few hrs. I feel bad because she is trippen but after she's fine so I don't know what's going on andy ideas

It's likely just part of her personality. Chi's are known to be skittish, hyper dogs.

If this is something you're concerned about then a trip to the vet to rule out any issues, is never a bad idea.