2008 Dodge Avenger Noise & shimmy

Shakes or Wobbles problem
2008 Dodge Avenger 4 cyl Front Wheel Drive Automatic 35k miles

When going 50 mph or more & I step on the breaks it shimmys the steering wheel shimmys also. Also, after driving about an hour in hot weather when I slow down & turn on roads, go over bumps turn corners I hear a thumping noise from front maybe somewhere around tires and feel it in the steering wheel, like a notching. Also, the air bag light has been coming on randomly, had it in the shop once at dealer they said they fixed it but now it comes on again. That dealer is now closed & out of business.