1999 ford windstar lx

sometimes when driving down the road, i smell something kinda like burning. the temp on the motor is fine, and i have looked under the hood, but found nothing that looked like it had been burnt

Very hard to guess what it might be....but first thing to look for is any signs of anything on the exhaust.....manifolds, catalytic converters......
Then, anything that seems to be acting up.

Also....look to see if the brake pressure switch is wet......a sign of it leaking....and they have been known to catch fire.
The brake pressure switch is located on the bottom of the brake master cylinder......the only thing that has electrical wires going to it.