Struggling with Interviews

Hii Guys,

I have around 4 years of experience in Salesforce and currently appearing in interviews to switch. I am good at technicals I answer all technical questions but when it comes to scenarios I fail to think of an answer even though I know how and what to use in the scenario but even though my brain gets stuck to think. I took too much time to think and was unable to answer properly and this is resulting me to get rejection. How can I overcome this situation if someone could help?