In hot weather speedometer stops off and on?

What I mean by heating up is the air temp. When it's 70 or above weather air temp it starts to act up. In the cold air everything is fine. I feel between air temp and vehicle operating temp is over heating what ever is the cause. Winter months never acts up. What I mean by acting up is : Speedometer starts to go up & down then goes to zero when at zero get a lag in performance and the engine lite comes on. Shut vehicle off it cools down everything goes back to normal engine lite is off runs great until it heats up again. Thank you for your time and help.