Hello farsk1 and welcome to CDFReaks!
Since your old stereo and car stereo plays this disks with no problems, it seem your portable CD player has problems to play burned CDs in a way.
So what can you do? Unfortunately you did not wrote the CD (or DVD) burner you used and the brand of your blank CD media.
First you should try to reduce the write speed of your burner to reduce the jitter. If your burner supports low burn speeds try 16x or 8x or 4x. You should try the lowest burn speed.
You can also try an other media brand like Verbatim. Noname disks are often poor quality and results problems.