Panasonic sky digital receiver turns itself off?

My Panasonic sky digital receiver turns itself off periodically with out warning and with no particular pattern. it could happen at any time from 2 hours use to 3-4 days use. To get the receiver to work again i may have to switch off the unit (at the plug socket) a number of times, swithing it on/off until eventually i get to see a channel. This doesn't seem like very good practice but it is the only way to get it back on. The unit is well ventilated so i dont believe it is over heating, then again what do i know! Thanks for any help.