I'm sorry to hear that you're having this issue with your television. I'm wondering if your cable is securely connected to the power supply, or if the power supply is securely connected to the wall - it may be a good thing to double check. (Sometimes the answers are that simple!)
If you're putting tension on the power cable, it may be loosening the connection inside of the television. If you're able to determine that it is happening only with the television, you may want to consider having your unit inspected by a technician. It may be that the cord may be disconnected from power supply internally, which can be fixed but would have to be done by a professional.
Keep me posted.