Sounds like either a problem with t-stat or circuit board. You need to test it when it happens to know for sure. The t-stat wire could have a bad connection also.

Thanks troys, The hard part is being there when it happens.

Depending of what type of indoor unit it is, it might be the fan relay or fan sequencer. There are a couple older indoor units that use sequencers that tend to stick. Might check that out.

Thanks "fluffy" I will certainly check that out as well.