Slipping gears

'95 Chrysler LeBaron, purchased for fun/convert. had it a month.

3 times, at complete stop within 1 mile of starting, gear has slipped. when i accel. out of stop . . . engine revs, tach revs, car coasts!

on my way to shop. sound serious or not? want to compare your thoughts to what the shop guys tell me.

thanks