2003 Nissan Altima 2.5 S

I have a 2003 Nissan Altima 2.5 S with approx. 78,000 miles on it.  Periodically, while driving on the freeway (or on city streets), it begins to jerk and the RPM gauge goes crazy for a second.  Any idea what this problem could be?  When the mechanic drove it, it didn't do it.  The check engine light is not on.  I thought it might be bad gas but I put in Chevron gas and it still did it.