My insignia model ns-ltdvd26 will cut off on its own. will turn right back on but will only stay on for a few minutes then cuts back off

Service manuals are hard to find now a days, even service parts. Check the link provided to find the main board for your LCD.
Finding the tuner alone might be hard or if you do, it might cost you the same as replacing the entire main board.
Let me know if you need further assistance. Insignia E23546 Main Board For Insignia E15318G NS LTDVD26 09 V260B1 LN1

The main digital board to your TV should be checked for fault.

IT MAY BE YOUR AUDIO/VIDEO CORD

the pic attached is an electrolytic capacitor, they come in different sizes and are usually blue, black and sometimes yellow. depending on manufacture.

most of the problems I have heard of tvs having problems with the electrolytic capacitors going bad. if you open the tv and see one of those swollen or leaking you need to replace them.

Issues of this type can generally only be resolved by repairs. Service can be obtained by carrying your TV in to the place of purchase.

You can order parts for your TV here. Select your exact model for available parts.

It is always recommended to ensure that your TV is powered down before connecting or disconnecting cables. Unfortunately, it is likely that your TV requires service for the power issue.

Here's the link to the LTDVD2609.
http://www.insignia-products.com/skins/skin_1/Topics/Documents/08-1044%20NS-LTDVD26-09_WEB.pdf

try to specify what kind of equipment is this please. Get the habit to give as much informations you can . Be accurate as possible

Manual is available at the following...

http://www.insignia-products.com/skins/skin_1/Topics/Documents/08-1044%20NS-LTDVD26-09_WEB.pdf