Don't paint it unless it's really beat up and rusty. It's a huge pain and either costs too much or just doesn't come out as good as you thought. Polish up the old paint complete with dings and scratches and ride it.

You need to make sure the ball bearings are correctly adjusted in the pedals, bottom bracket, hubs, and headset (steering.)

The brake pads might be dry.

Unless it's a singlespeed conversion, it could have dried up grease in the bearings which won't lubricate, but will just squish out of the way.

Everyone says to change out the cables and housings, but I never do and the old ones work fine.

The spokes need to be trued and tensioned. If you have a loose one, it will overstress the ones around it and they will soon fatigue and snap. There's also a chance that the rims are worn too thin from braking, but you would see deep gouges.

The frame or any of the components could be cracked and it needs checking.