Hi, I can help you with this.
The cycle on / off problem is a very common problem with these units, it is caused by a failure of power supply capacitors. The failure of these capacitors causes the 12 and 5 volt voltage lines to load down and the unit can not power on properly. This is a well knowned and documented problem among many Samsung LCD Tv's and your model is one them. Samsung recently setteld a class action law suit for this issue with these Tv's. The law suit allows you to get a free repair for this issue reguardless of the age of the Tv. In order to get free service you must do it through Samsung by calling (1800samsung) to set up service. Here is a link to more information about this issue with samsung Tv's and the class action law suit.
I can certainly do that but I would wonder why you would not want to pursue the repair for free from a qualified Samsung Tech. This has certainly been a major issue and samsung has been honoring the repair on theses units for many issues as the result of the law. This is certainly the first course of action I would recommend. Anyway The power supply capacitors in question on this unit would be the following.
LN52A750RF1 CM851 CM852 CM854 CM855 All capacitors should be replaced with 1000uf 25 volts. Of course if the capacitors do turn out to be ok the problem could certainly be caused by a main board. Testing would be needed to determin the cause, Main board LCD panel, etc. Certainly the first step would be to replace the capacitors and see if the issue is resolved. remember that any soldering that you do can be see by tech if you end up opting to go that route, most likely that will void any warranty that the unit may be eligible for.