@LarrytheStanimal you should do a separate warm up before you do your ramp test! Of course, to warm up yourself but more importantly to warm up your trainer.
From time to time I take data on my trainer…so I’ll have the trainer all set up and calibrated and I’ll have another powermeter zeroed and reading out on my headset. If I hop on the trainer and start pedalling there is a large difference between the rear-hub power (trainer) and the power at the pedal (powermeter). Sometimes it can be 20W but most of the time it’s between 10W & 15W. I can sit on the bike and spin at recovery watts & watch the difference go down, down, down until it settles in at some single-watt difference (this is 30s power I’m looking at). Depending on ambient temperature & the trainer that process can take as long as 20 minutes.
So if you are just hopping on the trainer cold and starting a ramp test definitely the first half of your ramp can be a little off. I like to do the LSCT Warm Up before a ramp test. That seems to do a good job of warming up my trainer and my body.
Also, ever notice that often your second interval feels easier than your first? 
That might be because it was!