My New Mifi just recently keeps switching off like 2-5 minutes after powering it on, I need help with this.

It's been over a year now since you asked this question, but I think this answer will benefit others.

Log in to your MiFi's dashboard at mtnbroadband.ng

Go to Device Settings>Advance Settings>Hibernation

Change the time from 5 minutes to 60 minutes.

That way your MiFi stays on for an hour before it hibernates.