Mystery instrument pannel short

I hadn’t run my Van for about 1 month.

I started it & the ABS light came on…

Brakes were OK… While I was driving it to shop, I noticed my speed, Tach, engine Temp, & gas gauge all were not working.

Then all of a sudden they worked & the ABS light went off. What could be causing this?

Most likely, you have a marginal wheel speed sensor.
Also, it seems that you may not understand what the ABS warning light means. It does not indicate any problem with your normal brakes. It indicates that you will not have skid prevention in a panic stop.

I suspect that all the things you mentioned are tied to a common power source, possibly a ignition switch contact problem or something else in the power lead so I recommend checking the power to those things. The BCM module could also be a factor with this trouble. I like Tardis’s suggestion but the only thing I question about it is your mention of the fuel gauge and engine temp with the other things. I don’t think they have anything to do with the speed sensors so I think it is a power problem. There may be a faulty connection at the dash panel also. Using a screwdriver handle to tap on suspected trouble areas may show up the trouble spot.

Try cleaning the ground connection for the instrument panel.