Blower motor cuts in and out no matter what fan speed it is on

Hello,

Sounds like this could be a connection issue or internal loose or worn components for the blower motor or the resistor.

A good first step would be to access the blower motor and make sure the wiring harness is secured.
Look for any corrosion or pushed out or burn pins.
Over time due to a loose connection, you will have burnt pins.

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

I have attached diagrams for your reference.

Please let me know what you find or if you have any questions.
Thank you.

Okay, thank you. I will check it in the morning. The blower sounds good and works at every speed. It will come on soon as I start truck and sometimes it will work fine and other days it will just cut in and out and rev up and down. I can smack it when it cuts off and it will come right on and work.

The symptoms that you have sound like a loose connection somewhere.
Let me know what you find out.