Skateboard stop working for a while when applying brakes and wobbling

I'm new to skateboarding, however after a few hours of riding I get accustomed to it and slowly gaining confidence. As I'm riding, I noticed two things that seems to be odd hence this question.

• I just want to know if it's normal that the skateboard seems to stop working after applying brakes. After the a few minutes the skateboard works again but not after a couple of minutes. Is this normal? Because I have to go to side of the road and wait for it become alive?

• Second thing, The rear wheels seems to wobble. On slow speed, I cant barely feel it. But when it hits 15-18km/h then the wobble becomes significant as I need to correct the board to keep me straight. I feel very uncomfortable specially when I have to correct my board to stay true to the road.

Thanks for any response and inputs.