1994 4t60E
It only happens every so often but, starting out in first sometimes I get a loss of power at about 2000 rpm/ 10-15mph for about 5 secs, and not sure if this is related (probably is) but on the highway sometimes doesn't shift between 3rd and 4th and at the same time I have no power till about 3000 to 4000 rpm.

any ideas?