Sounds like lovely (from a glider pilots point of view) thermals going through.
I the air you will feel them as up / down draught.
On the ground you will feel them as gusts - lasting from a few seconds to many minutes.
You could try visiting your local gliding club and explaining your problem - any decent gliding instructor will be able to explain precisely what is going on.
While this may not explain with how to handle them in a C152, understanding the air you are flying through will certainly help.
OC619
P.S. Be prepared, if you visit a gliding site, to be sucked into "pure" flying - it happened to me
