1996 Chevy Silverado Please Help!

Electrical problem
1996 Chevy Silverado V8 Two Wheel Drive Automatic 140k miles

Hi, I have a 96 chevy silverado, short bed, regular cab, 2 wd. My trucks has been having some electrical problems such as, lights inside dash and running lights flickering on and off and it makes a sort of buzzing noise when it does this, as well as my power door controls sometimes work and other times dont, my cd player also comes has the same problem, also it has a hard time starting here and there and sometimes when it starts after a loud noise from the starter it sounds like it over starts and makes a loud wind up noise upon firing. All these problems come on and off randomly and seem to go hand and hand. I'm wondering where I should start and what I should check before I spend all my money to get it looked at elsewhere. Thank you so much for the help!