Tachometer dropping to zero while driving

While I'm driving my tachometer will drop to zero, I can either wait and let my speed lower and it fix it's self or I can immediately give it gas and it'll go back to normal. Any suggestions on what's going on?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0