1999 Subaru Forester compressor possible short cycling

Hello,

I recently charged my air conditioner with r-134a refrigerant because the gauge said it was a little low. Now, it is fully charged, but I was driving on the freeway today, cruising at about 80 mph, about 75Ëš outside, and noticed that every 15 seconds or so the car would jerk slightly (not very much, but noticeable). I'm pretty sure that it jerks every time the compressor turns on. While feeling the air coming out of the vents, it is very cold when the compressor turns on, but that doesn't seem to last very long because it cycles off so quickly. It just gets very cold, then sort of cold maybe 10 seconds later, then very cold again. Is this abnormal? I don't remember it happened before I added the r-134a, so I'm wondering if there's something I did wrong. The can that I used did not have any AC oil in it, so could this be the problem? Should be car be jerking like that every time the compressor turns on?

Thanks!