Mac turning off erratically but working fine in Safe Mode.

I have MacBook Air 2017, currently on macOS High Sierra 10.13.6. For

last two weeks my laptop is misbehaving - the screen just pops shut

without warning. It wakes up whenever it wishes to, for a second then

again shuts down. Although it doesn't need reboot, so problem is only

with screen. I get this notification just before screen shuts -

USB Accessories Disabled - unplug the accessory using too much power to re-enable USB devices.

I tried resetting SCM, didn't work. Went to Apple service store - but

he is a fool and says motherboard and screen both need to change. I

brought back my laptop and opened it in safe mode. It works fine. In

safe mode I deleted login items and rebooted in normal mode. Again the

problem occurred.

So at this point my laptop is working (using same laptop to write

this..) only in safe mode. This is my first ever apple product and I am

nowhere near being an expert at troubleshooting Apple products. Please

suggest what can be the best course of action.