Then the light goes off and the pressure goes back up.
Why is it doing that??? It does that usually at start or just after starting the engine.
Also, my blinker is turned on, then it stops blinking completely until the next time I use it and it happens again. It happens on both turns.
Any ideas???

 

Sounds like a possible wiring problem, any chance of a mouse getting up in your truck?

 

Poor ground somewhere?

 

Where can I first look then????
Should I check a fuse box?
What about the blinker???

 

Two separate issues (hard to tell, your description is not clear).

1. Replace the oil pressure sending switch.

2. As for the blinker, check your exterior bulbs.