2014 F150 Platinum with 77k miles bought 1 month ago: Lately, when the truck sits over night, I get in, let it warm up for 10 ish minute, foot on brake, put it in drive, take foot off brake truck begins rolling i ease onto the gas and it accelerates and when it hits anywhere from 5-15 mph, it locks up my wheels and it comes to a screeching halt. Foot’s not on gas or brake and in drive yet the front end dips as if the brakes are activated, brake pedal is not stuck at all, does not move. No lights come on. put it in park then back in drive and it’s a 50/50 chance it does it again. but if you shut it off and turn it back on it won’t do it again. Also once you get going, it typically does not do it. the consistent thing is whenever it happens it’s always from a stop to beginning of acceleration

 

If anybody did brake work on the vehicle just before you purchased it , they may have allowed air to get into the system, we don't know.

If the brake master cyl was replaced and not installed properly, there could be a problem with the rod between the booster and master cyl.
Best to have a good shop check the entire brake system..