Soo here recently iv been having some issues with my 03 Blazer. When I turn the car on cold start the ABS light comes on. As I accelerate down the road the MPH needle shakes until it hits 45. When I go below 35 after already going above it the park brake light comes on it will accelerate but wont switch gears. After it warms up it switches gears, the park brake light goes off, and eventually the ABS light goes off. Iv searched online but cant find any clear answer.

 

I'll give this a bump with some general advice. See about getting a scan done of any OBD codes. With the symptoms you listed, you'll need to find a code reader that has access to more than just the basic engine related ones. Thankfully auto parts stores like O'Reilly's and Autozone normally have people with the necessary readers. With this information people on the forum who are more knowledgeable than I can help you diagnose what is going on.

My first impression, and I could be wrong, is that it is unlikely that there is one specific cause for your issues.