To help you tune up I have provided a number of tuning note tracks here. I use A=440Hz as the default tuning on my website.
Most of my tracks start with 2 seconds of silence at the beginning and end with 4 seconds at the end.
However, it is quite easy to add more silence between the tracks, by adding 'silence' tracks to your playlist. This can be especially useful if you are playing many pieces back to back and want more space between the movements.
Here are some silent tracks that you can use.
Another option is to use an audio editor such as Audacity (see below) to insert a specified length of silence at the start or finish. The advantage with an audio editor is that you can also use it to add silence in the middle of a track, for example if you want more time to play a cadenza or need a pause somewhere. Audacity has it's own 'generate silence' option which can be found in the menu options.
Many of the works on my website correspond to scores that can be found on IMSLP. So long as you adhere to the copyright rules relevant to your country, you may download and practice from the scores on the site.
Wave editors - As mentioned above, Audacity® and other audio (wave) editors can be used to create silence or pauses within a track, and by using the 'mute' function you can also remove click-beats as well. By cutting and pasting, you can generate loops to practice with, or add your own repeats if I have omitted them.
Software to modify tempo and pitch - For changing the speed of these tracks, I recommend The Amazing Slow Downer to change tempo without altering pitch. A good alternative is Song Surgeon 4, which also includes a wave editor and other features. Both programs can also change the pitch of the track instead, for example if you need to play up a tone.
There may be other free and commercial software you can uncover from doing a quick web search. Obviously all software must be downloaded at your own risk, and please be wary of certain free software products that may potential harm your computer.