Hi!

Something in your TV is shorted or the regulation in the power supply has
become faulty.

What you are seeing (and hearing) is the power supply attempting to come up
and then shut down again. Normally this happens when the outputs of the
supply are shorted or even overloaded. Since you mentioned seeing channel
numbers flicker on and off on the set, it is very possible that the power
supply itself is where the fault lies and that the rest of the set is fine.
As a wild guess, I would say that bad capacitors in the power supply are
likely.

If you don't know where to start and you want to have the TV fixed, then it
might be advisable to take it to a shop and get an estimate on repair.
Provided the TV was working well prior to its failure the cost of repair may
be worth it. If you want to learn to repair electronics, I wouldn't start
with a TV set. There is just too much inside that can give you a nasty
surprise or even ruin the whole day (and a lot more) if you don't know
what's all going on in there.

William