A flickering ceiling light can be caused by a loose light bulb in the socket or it could be the light fixture is bad or a wire is loose to the light fixture or the switch is bad or a wire to the light switch is bad.
First I would make sure the light bulb in the light fixture is tight in the socket and not loose as the loose connection of the light bulb can cause the bulb to flicker.
A loose wire can also cause the bulb in the fixture to flicker so check that out as well.
If you're not comfortable working with electricity then hire a handyman or electrician to check out the problem and it could be that the light fixture needs replaced.
If the LED bulb is flashing on and off then it's the light bulb going out but if the light is flickering constantly you have either a bad light fixture or a loose wire connection or the socket is bad in the light fixture.
If the light fixture is the type with a ballast then it could be the ballast going bad causing the light to flicker on and off or it could be the bulb.