A couple of guess, mind you...
1. The easisest and hopefully whats wrong, a new clean gas filter.
2. The brake pads have projections through the pad portion, so that when the pad gets too thin, the metal projection scrapes the drum or rotor. Continued use will require new drums & rotors. Expensive.
3. Just a guess,, maybe a wheel bearing or again could be the break pads just litely rubbing on something.
I still take my vehicles to the garage for major repairs, minor ones, I have the mechanic tell me what the problem is, he tells me if I can fix it.