1998 MTD Yardman 694 Hydrostatic only works after warmed up

Have a 1998 MTD Yardman 694 with hydrostatic transmission which won't move when first started. If I push the transaxle speed selector forward or reverse, it takes 15-30 seconds before it will even begin to move. After that, it works perfectly with plenty of speed and will tackle a hill with no problem. Once the mower is shut off and sits for a couple hours, ample time to fully cool down, it will have the same moving issue again after restart. Hold the lever in place for half a minute, and it's ready to mow and go again. It's acting like the fluid needs to be warmed up/ cycled first, or it's not gaining pressure for a while?

Have you ever changed fluid? post your MTD yardman model & serial numbers, thanks.

https://www.mtdproducts.com/equipme...lNumber=13BX694G401&serialNumber=1K02F8H30057

1998 MTD Yardman 694 Hydrostatic/ Model: 13BX694G401 / Serial: 1K028H 30052

Fluid has never been changed.

One simple thing to try, when you let off the brake pull the foot lever back with the top of your foot. Could be the belt tensioners are bound up some and not tightening the drive belt? Not for all models but worth a try.

Excellent idea about the brake, and I had already tried that. I should have previously mentioned the belt has proper tension and the lever neutral position is correct. It's only on initial cold startup this problem exists. After that, the speed control will work flawlessly all day long, or until the transmission has time to cool off. If I shut the mower off after using it for a couple of minutes or even a few hours, then come back to it later within one hour (still warm) and restart it, the transmission will work perfectly with no delay. I've seen several people refer to dirty or low fluid level causing it to keep getting slower or come to a stop after it gets hot, but mine is doing the exact opposite of that. Done a ton of research and haven't come across anything similar.