Good afternoon my name is ***** ***** I will assist with your query.
This sounds like a power board failure, you will probably find a component on the board which controls power to the TV is starting to fail and hence your getting an intermittent fault, this is rather common in TV's which are 5 years and older.
The fault will get progressively worse, to the point where the TV will not turn on (however this could take days, weeks or months, such is the nature of failing components).
I would suggest your best option is to take the TV to a repair centre they can then isolate the fault, and quote for repair, often a simple power board issue can be resolved for £100.
Should you wish to go down this route, please provide me with your postcode and I can recommend a suitable service centre in your area.
I would highly recommend Glynne St Electrics on 13A Glynne Street, Bolton, BL4 7DN, they are a good 10 mile from you, but they dont charge for diagnosing the fault and quoting for repair, and very trustworthy.