battery drain immediately

It could be that your battery comes to the end of its lifetime. See this article on battery health on iPhones: https://support.apple.com/en-us/HT208387

Before sending your iPhone for a battery repair (which might be necessary), I recommend trying to restore your iPhone to factory settings and seeing if the problem persists. A battery repair usually isn't that expensive, and with an older iPhone like yours is a very likely maintenance need.

What is the battery health?

Hi senthil1975

I would suggest you check your battery health first. To get there first go to Settings > Battery > Battery health. This should tell you your battery capacity and how good it is.