lowrance hook2/7"

screen randomly loses image,does not lose power. I turn off power and restart , sometime it returns to normal, sometime it restarts in the demo mode option which might indicate a hard reset has occurred. Any thoughts?

Make sure your power connection in the back is pushed in and secured. Screens going off and back-on sometimes can be battery. I would call Lowrance if you can't get it to working.
When & where did you purchase the unit?

I had a Hook2 5” that was bad from day 1. I had it replaced.

The plugs in the back of the unit have to be seated well. If they are not all the way in, they can back out just enough to lose connection.